1950s Engagement Rings
311
to
16
Item Location
155
154
4.25
4.5
4.75
5
5.25
5.5
5.75
6
6.25
6.5
6.75
7
7.25
7.5
7.75
8
8.25
8.5
8.75
9
54
471
6,284
14,791
261
399
1,017
610
285
311
177
173
202
281
16
6
4
2
2
2
162
148
1
176
158
92
85
41
305
55
53
26
19
87
34
33
22
17
to
104
34
13
5
2
1
Period:1950s
Vintage Three-Ring Diamond White Gold Engagement Ring Set Size 8.75
Located in Los Angeles, CA
Vintage three-ring diamond engagement ring set mounted in white gold circa 1950. Love it because it caught your eye, and we are here to connect you with beautiful and affordable je...
Category
Modern Vintage 1950s Engagement Rings
Materials
Diamond, 14k Gold, White Gold
GIA Certificate 1.26 Carat Art Deco Style Engraved Ring Side Diamonds
Located in Los Angeles, CA
This is a 14k white gold ring with a GIA 1.26 carat Old European cut diamond center, K color, VS2 clarity. The ring has an engraving inside its shank with 18 single cut diamonds weig...
Category
Art Deco Vintage 1950s Engagement Rings
Materials
Diamond, 14k Gold
Tiffany & Co. 3.94 Carats Round Brilliant Diamond Platinum Engagement Ring GIA
Located in Philadelphia, PA
Featuring a round brilliant cut diamond weighing 3.59 carats - I color with SI1 clarity
Basket set by wide prongs and flanked by cathedral shoulders
Bar set by tapered baguette cut...
Category
Retro Vintage 1950s Engagement Rings
Materials
Diamond, White Diamond, Platinum
Retro GIA 4.15 Carat Round Brilliant Cut Diamond Platinum Engagement Ring
Located in Beverly Hills, CA
One Retro GIA 4.15 Carat Round Brilliant Cut Diamond Platinum Engagement Ring. Featuring one GIA certified 4.15 carat accompanied with certificate #2221185211 stating the diamond is ...
Category
Retro Vintage 1950s Engagement Rings
Materials
Diamond, Platinum
Platinum Single Stone 1.50 Carat Diamond Engagement Ring
Located in Firenze, IT
Claw set with an old cut diamond weighing approximately 1.51 cts, to shoulders engraved and plain hoop.
Mounted in platinum.
Weight: 3,89 gr
Finger size: 6
Category
Retro Vintage 1950s Engagement Rings
Materials
Diamond, Platinum
Retro Certified 8 Carats Non heated Ceylon Sapphire Diamonds Platinum 18 Carats
Located in Paris, FR
Exceptional white gold and platinum ring set with an oval Ceylon sapphire and 6 brilliant cut diamonds.
Dimensions of the sapphire : 13.5 x 11.40 x 6.58 mm, (0.525 x 0.449 x 0.259 i...
Category
Retro Vintage 1950s Engagement Rings
Materials
Diamond, Sapphire, Platinum
Retro Diamond Platinum Engagement Ring
Located in Beverly Hills, CA
One Retro Diamond Platinum Engagement Ring. Featuring one transitional cut diamond weighing approximately 0.65 carat, graded I color, SI1 clarity. Accented by 20 single cut diamonds ...
Category
Retro Vintage 1950s Engagement Rings
Materials
Diamond, Platinum
Art Deco GIA Diamond Platinum Engagement Ring
Located in Beverly Hills, CA
One Art Deco GIA Diamond Platinum Engagement Ring. Featuring one GIA certified 1.48 carat old European cut diamond accompanied with certificate #1226185806 stating the diamond is J c...
Category
Retro Vintage 1950s Engagement Rings
Materials
Diamond, Platinum
1.24 Carat Diamond and Sapphire Platinum Engagement Ring
Located in Jesmond, Newcastle Upon Tyne
This stunning, fine and impressive blue sapphire and diamond engagement ring has been crafted in platinum.
A stunning vintage 1950s 0.98 Ct Transitional modern brilliant round cut d...
Category
Vintage 1950s Engagement Rings
Materials
Diamond, Blue Sapphire, Sapphire, Platinum
Vintage 1950s 1.34 Carat Aquamarine and Diamond White Gold Cluster Ring
Located in Jesmond, Newcastle Upon Tyne
A fine and impressive 1.34 Ct aquamarine and 0.96Ct diamond, 14k white gold cluster style cocktail ring; part of our diverse vintage jewelry and estate jewelry collections.
This fin...
Category
Vintage 1950s Engagement Rings
Materials
Aquamarine, Diamond, Gold, 14k Gold, White Gold
Vintage 2.20Ct Diamond and White Gold Cluster Ring, Circa 1955
Located in Jesmond, Newcastle Upon Tyne
A stunning, fine and impressive vintage 2.20 carat diamond and 14 carat white gold cluster style dress ring; part of our diverse antique jewellery and estate jewelry collections
Thi...
Category
Vintage 1950s Engagement Rings
Materials
Diamond, Gold, 14k Gold, White Gold
French 1950s 1.10 Carat Diamonds 18 Karat White Gold Jean Eté Ring
Located in Poitiers, FR
Ring in 18 karat white gold, eagle's head hallmark, and platinum, dog's head hallmark.
The head of this antique ring is made of openwork stepped gold threads, set with brilliant-cut ...
Category
Retro Vintage 1950s Engagement Rings
Materials
Diamond, White Diamond, Gold, 18k Gold, Platinum, White Gold
Vintage 1950s Sapphire and Emerald Diamond and Platinum Twist Ring
Located in Jesmond, Newcastle Upon Tyne
An impressive vintage 0.47 carat sapphire and 0.50 carat emerald, 0.77 carat diamond and platinum twist ring; part of our diverse gemstone jewelry and estate jewelry collections.
Th...
Category
Vintage 1950s Engagement Rings
Materials
Diamond, Emerald, Sapphire, Platinum
Vintage 1950s 1.29Ct Oval Cut Emerald 2.02Ct Diamond White Gold Cocktail Ring
Located in Jesmond, Newcastle Upon Tyne
A stunning, fine and impressive vintage 1.29 carat natural emerald and 2.02 carat diamond, 18 karat white gold, multi strand twist ring; part of our vintage jewelry and estate jewelr...
Category
Vintage 1950s Engagement Rings
Materials
Diamond, Emerald, 18k Gold, White Gold
Blue Aquamarine Ring, Vintage Ring, 14K White Gold, Circa 1955, 1.52 Carats
Located in Austin, TX
Aquamarines are said to give off tranquility and serenity energies. The calming blue color goes perfectly with the white gold of the ring. This subtle, but fun design makes a perfect...
Category
Retro Vintage 1950s Engagement Rings
Materials
Aquamarine, 14k Gold, White Gold
1950s Engagement Ring with Spiral Setting
Located in New York, NY
The beautiful engagement ring is finely crafted in 14k white gold and diamonds weighing approximately total of 0.80 carat.
Easy to resize.
Circa 1950's.
Category
Vintage 1950s Engagement Rings
Materials
Diamond, 14k Gold
Retro GIA 3.25 Carat Old Mine Cut Diamond Platinum Engagement Ring
Located in Beverly Hills, CA
One Retro GIA 3.25 Carat Diamond Platinum Engagement Ring. Featuring one GIA certified 3.25 carat old mine cut diamond accompanied with certificate #6214084514 stating the diamond is...
Category
Retro Vintage 1950s Engagement Rings
Materials
Diamond, Platinum
Midcentury Platinum Euro Cut Diamond Engagement Ring
Located in Lexington, KY
This beautiful platinum engagement ring features a stunning 0.80ct European-cut diamond with three sparkling round diamonds on each shoulder. Approximate 0.90 cttw for all the diamon...
Category
Vintage 1950s Engagement Rings
Materials
Diamond, Platinum
French 1950s Diamonds 18 Karat White Gold Daisy Ring
Located in Poitiers, FR
Ring in 18 karat white gold, eagle head hallmark and platinum, dog head hallmark.
Round in shape, this daisy ring is adorned with a brilliant-cut diamond on a surround of other diamo...
Category
Retro Vintage 1950s Engagement Rings
Materials
Diamond, White Diamond, Gold, 18k Gold, White Gold
Retro GIA 3.03 Carat Pear Shape Diamond Platinum Engagement Ring
Located in Beverly Hills, CA
One Retro GIA 3.03 Carat Pear Shape Diamond Platinum Engagement Ring. Featuring one GIA certified 3.03 carat pear shape diamond accompanied with certificate #2221134204 stating the d...
Category
Retro Vintage 1950s Engagement Rings
Materials
Diamond, Platinum
Cartier 1950's 1.76 Carats Diamond Emerald 18 Karat Two-Tone Bypass Ring GIA
By Cartier
Located in Philadelphia, PA
Bypass style ring centers an oval brilliant cut diamond weighing 1.16 carat - I color with VS1 clarity
Set East to West and flanked by rectangular cut emeralds weighing in total app...
Category
Retro Vintage 1950s Engagement Rings
Materials
Diamond, Emerald, 18k Gold
Vintage Old Euro Cut 3-Stone Ring EGL Certificate G SI3 Total Weight 1.67 Carat
Located in Los Angeles, CA
Vintage Old Euro Cut 3 stone ring EGL G SI3 total weight 1.67cts., containing 1 euro cut diamond; color EGL Certificate color "G", clarity SI3 and weight 1.09cts. with 2 side euro cu...
Category
Art Deco Vintage 1950s Engagement Rings
Materials
Diamond, 14k Gold
1950s 3.03 Carat Diamond and Platinum Solitaire Ring
Located in Jesmond, Newcastle Upon Tyne
A stunning, fine and impressive vintage 3.03 carat diamond solitaire ring in platinum; part of our vintage engagement ring collections.
This stunning vintage solitaire ring has been...
Category
Vintage 1950s Engagement Rings
Materials
Diamond, Platinum
Emerald and Diamond Engagement Ring Platinum Art Deco Style, Circa 1950
Located in London, GB
An emerald and diamond platinum engagement ring in an Art Deco style, circa 1950
This ring is centrally set with an beautiful 2.07 carat emerald cut emerald which is claw set in pla...
Category
Art Deco Vintage 1950s Engagement Rings
Materials
Diamond, Emerald, Platinum
0.60 Carat Diamond Engagement Ring Vintage 1950s White Gold
Located in Milano, IT
Antique and harmonious diamond solitaire engagement ring dating back to the 1950s in 18 carat white gold with a round brilliant diamond 0.60 carat, IGI certified, color K/L clarity S...
Category
Vintage 1950s Engagement Rings
Materials
Diamond, 18k Gold, White Gold
1950s 5.70Ct High Zircon and 3.15Ct Diamond White Gold Cocktail Ring
Located in Jesmond, Newcastle Upon Tyne
A stunning vintage 5.70Ct high zircon and 3.15Ct diamond, 18k white gold dress ring; part of our diverse vintage jewelry and estate jewelry collections.
This stunning, fine and impr...
Category
Vintage 1950s Engagement Rings
Materials
Diamond, Zircon, 18k Gold, White Gold
5.28 Carat Purple Pink Natural Sapphire Diamond Platinum Engagement Ring
Located in Stamford, CT
Natural GIA certified purplish pink 5.28ct Sapphire diamond engagement ring. Original 1950-1960 Platinum ring with tapered baguette Diamond accents. In both Diamond and Sapphire purp...
Category
Vintage 1950s Engagement Rings
Materials
Diamond, Pink Sapphire, Platinum
Diamond Estate Wedding Set, 1.06 Carat Total Wt, Ring or Adjustable
Located in Austin, TX
14K White Gold Wedding Set-Circa 1950.
6.48 grams (together), band weighs 3.1 grams, ring weighs 3.38 grams
Ring size 6 1/2
Wedding set has approximately 1.06 carat total diamond w...
Category
Retro Vintage 1950s Engagement Rings
Materials
Diamond, 14k Gold, White Gold
1950's Mid-Century 0.65 Carat Diamond Platinum Engagement Ring
Located in Philadelphia, PA
Centering a transitional cut diamond weighing approximately 0.45 carat - H/I with VS clarity
Set low in a square form head in an East/West mounting designed as a buckle motif
Accen...
Category
Retro Vintage 1950s Engagement Rings
Materials
Diamond, White Diamond, Platinum
Vintage French GIA 3.17 Carat Old European Cut Diamond Platinum Engagement Ring
Located in Beverly Hills, CA
Vintage French GIA 3.17 Carat Old European Cut Diamond Platinum Engagement Ring. Featuring one 3.17 carat old European cut diamond accompanied with certificate #5221146707 stating th...
Category
Retro Vintage 1950s Engagement Rings
Materials
Diamond, Gold, 18k Gold, White Gold, Platinum
Boucheron Natural Untreated 12.80 Carat Sapphire Diamond Ring Set in Platinum
By Boucheron
Located in London, GB
A truly exceptional Boucheron Art Deco inspired sapphire and diamond ring set in platinum, circa 1950.
The ring is set to its centre with an impressive natural, untreated 12.80 cara...
Category
Art Deco Vintage 1950s Engagement Rings
Materials
Diamond, Sapphire, Platinum
Retro GIA 6.16 Carat Antique Oval Cut Diamond Platinum Engagement Ring
Located in Beverly Hills, CA
One Retro GIA 6.16 Carat Antique Oval Cut Diamond Platinum Engagement Ring. Featuring one GIA certified 6.16 carat antique oval diamond cut accompanied with certificate #2185530527 s...
Category
Retro Vintage 1950s Engagement Rings
Materials
Diamond, Platinum
3.94 Carat Ruby and Baguette Diamond Ring
Located in Carmel-by-the-Sea, CA
Platinum ring, classic style, with hints of "special"… Immediately notice the intense, rich magenta color of the 3.94 carat ruby… Look closer to appreciate the separated prongs, the ...
Category
Vintage 1950s Engagement Rings
Materials
Diamond, Ruby, Platinum
2.70 Carat Diamond White Gold Platinum Set Twist Ring
Located in Jesmond, Newcastle Upon Tyne
A stunning antique 2.70 carat diamond and vintage 15 karat white gold, platinum set twist style dress ring; part of our diverse diamond estate jewelry collections.
This stunning, fi...
Category
Vintage 1950s Engagement Rings
Materials
Diamond, 15k Gold, White Gold, Platinum
6.75 Carats Sapphire and 2 Carats Diamonds French Vintage Ring
Located in Saint-Ouen, FR
One very beautiful ring, made in France circa 1950.
The central sapphire is big, 6.75 carats and has intense blue color, the clarity is very good. It is certified from Ceylan ans No ...
Category
Vintage 1950s Engagement Rings
Materials
Diamond, Sapphire
Mid-Century 2.75 Carats Diamond Platinum Engagement Ring GIA
Located in Philadelphia, PA
Featuring a round brilliant cut diamond weighing 2.25 carats - F color and SI2 clarity
Prong set and flanked by cathedral shoulders bar set with tapered baguette diamonds
Weighing ...
Category
Retro Vintage 1950s Engagement Rings
Materials
Diamond, White Diamond, Platinum
English Emerald and Diamond 18k Gold Cluster Ring, Mid 20th Century
Located in St. Catharines, ON
A beautiful square cut emerald and diamond cluster ring set with a vivid green emerald, surrounded by twelve bright diamonds, in millegrain setting, mounted in 18k white gold.
Mid 2...
Category
Art Deco Vintage 1950s Engagement Rings
Materials
Diamond, Emerald, 18k Gold, White Gold
Bulgari Very Light Pink 4ct Diamond Ring, ca. 1950s
By Bvlgari
Located in Idar-Oberstein, DE
Important Bulgari Old-Cut Pearshape Pink Diamond Ring, ca. 1950s
An important ring by Bulgari, centring a rare very light pink coloured old-cut pearshape diamond of 4.22 carats (GIA...
Category
Retro Vintage 1950s Engagement Rings
Materials
Diamond, Platinum
Vintage Emerald and Diamond 18 Carat White Gold Cluster Ring
Located in Chipping Campden, GB
The gorgeous 60pt emerald perched on top of this simple claw setting is fabulous bright green. Complimenting the stone perfectly is a halo of bright white diamonds. The ring is model...
Category
Modern Vintage 1950s Engagement Rings
Materials
Diamond, Emerald, White Gold
5.44 Carat Colombian Emerald and Diamond White Gold Ring
Located in New York, NY
A stunning 5.44 carat rectangular step cut Colombian emerald and diamond white gold ring, made circa 1950. CISGEM certificate available.
Category
Vintage 1950s Engagement Rings
Materials
Diamond, Emerald, White Gold
Vintage 6.75cts Diamond Emerald Platinum Engagment Cocktail Ring
Located in Miami, FL
Bring a touch of green to your life with this Vintage Diamond & Emerald Elegant Cluster Dome Cocktail Engagement Ring weighing approximately 8.2 grams.
Crafted in solid platinum, t...
Category
Art Deco Vintage 1950s Engagement Rings
Materials
Diamond, Emerald, Platinum
0,60 carat old cut Diamond, 18 Karat White Gold Ring
Located in Marcianise, Marcianise (CE)
SHIPPING POLICY:
No additional costs will be added to this order.
Shipping costs will be totally covered by the seller (customs duties included).
Elegant ring in 18 karat white go...
Category
Retro Vintage 1950s Engagement Rings
Materials
Diamond, 18k Gold, White Gold
Old European Cut 0.70 Carat Round Diamond Ring 14 Karat White Gold
Located in Miami, FL
Old European Cut 0.70 Carat Round Diamond Ring 14k White Gold. Circa Art Deco 1950’s. Features 0.60 carat center diamond K/VS surrounded by 12 round cut diamonds totaling 0.10 carats...
Category
Art Deco Vintage 1950s Engagement Rings
Materials
Diamond, White Gold
3.93 Carat Royal Blue Sapphire Marquise Diamond Platinum Engagement Ring
Located in Stamford, CT
Royal blue oval 3.93ct Sapphire and diamond engagement ring. Designed in a handmade solid Platinum setting with a Marquise diamond halo. GIA Certified Simple heat only, no other enh...
Category
Vintage 1950s Engagement Rings
Materials
Diamond, Sapphire, Platinum
1.44 Carat Natural Ruby and Diamond Coronet Cluster Platinum Engagement Ring
Located in London, GB
Lovely coronet set cluster engagement ring featuring a 1.44ct natural oval red ruby, claw set in the centre of ten round brilliant cut diamonds with an approximate total diamond weig...
Category
Victorian Vintage 1950s Engagement Rings
Materials
Diamond, Ruby, Platinum
1950s French Diamond and Yellow Gold Twist Solitaire Ring
Located in Jesmond, Newcastle Upon Tyne
A fine and impressive vintage French 0.51 carat diamond and 18 karat yellow gold solitaire twist ring; part of our diverse jewelry and estate jewelry collections
This fine and impre...
Category
Vintage 1950s Engagement Rings
Materials
Diamond, 18k Gold, Yellow Gold
1950s 1.74 Carat Oval Cut Emerald and Diamond Yellow Gold Cluster Ring
Located in Jesmond, Newcastle Upon Tyne
A stunning and impressive vintage 1.74 carat Colombian emerald and 0.80 carat diamond, 18 karat yellow gold, 18 karat white gold set ring; an addition to our antique jewelry collecti...
Category
Vintage 1950s Engagement Rings
Materials
Diamond, Emerald, 18k Gold, Yellow Gold
1950s 3.23 Carat Emerald and 3.91 Carat Diamond Platinum Cocktail Ring
Located in Jesmond, Newcastle Upon Tyne
A stunning vintage 3.23 carat emerald and 3.91 carat diamond, platinum twist style dress ring; part of our diverse gemstone jewelry and estate jewelry collections.
This stunning, fi...
Category
Vintage 1950s Engagement Rings
Materials
Emerald, Diamond, Platinum
Vintage French GIA Antique Cushion Cut Diamond Solitaire Engagement Ring
Located in Beverly Hills, CA
One Vintage French GIA Antique Cushion Cut Diamond Solitaire Engagement Ring. Featuring one GIA certified 1.22 carat antique cushion cut diamond accompanied with certificate #7321625...
Category
Retro Vintage 1950s Engagement Rings
Materials
Diamond, Platinum
Art Deco Style Ruby Diamond Platinum Engagement Ring
Located in Brunswick, ME
This beautiful Art Deco Style two stone cross-over engagement ring features two oval natural rubies weighing approximately 1.06 carat, both in a triple four claw open back setting. T...
Category
Art Deco Vintage 1950s Engagement Rings
Materials
Diamond, Ruby, Platinum
Vintage 1950s 2.10 Carat Round Diamond Ring with Sapphires and Diamonds
Located in Boston, MA
Vintage 2.10ct European Cut Round Diamond Ring from the 1950’s. The diamond is a K color and VS2 clarity. A European cut diamond is set on either side along with an additional 12 ful...
Category
Modern Vintage 1950s Engagement Rings
Materials
Diamond, Sapphire, Platinum
Vintage GIA F VS2 Mid-Century 1.58 Ct. Emerald Cut Engagement Ring in Platinum
Located in New York, NY
You will get lost in the sharp facets of this sleek mid-century engagement ring. An icy-white emerald-cut center stands bright in the center, flanked by two delicate channel-set bagu...
Category
Vintage 1950s Engagement Rings
Materials
Diamond, Platinum
Vintage 3.18ct Oval Blue Sapphire and Diamond Platinum Deco Engagement Ring
Located in London, GB
This beautiful Art Deco style, 1950's engagement ring features a natural royal blue oval sapphire weighing 3.18ct in a four claw open, back setting. The sapphire is accompanied by tw...
Category
Art Deco Vintage 1950s Engagement Rings
Materials
Diamond, Sapphire, Blue Sapphire, Platinum
Elegant Emerald-Cut Diamond Ring with Side Baguettes Set in Platinum
Located in Miami, FL
An elegant and classic engagement ring featuring a center diamond weighing 2.02 carats emerald cut diamond graded K color and VS2 clarity accompanied with an EGL report. The center d...
Category
Modern Vintage 1950s Engagement Rings
Materials
Diamond, Platinum
GIA 1.55ct Natural No-Heat Orangy Red Spinel and Diamond 3-Stone Vintage Ring
Located in New York, NY
Red SPINEL, the gem of the many royals - a Very Sparkly Alternative for the Modern Engagement ring. If you are one of the many people interested in something other than a colorless d...
Category
Vintage 1950s Engagement Rings
Materials
Diamond, Spinel, 18k Gold, White Gold
Antique and Vintage 1.68 Carat Diamond and White Gold Cocktail Ring
Located in Jesmond, Newcastle Upon Tyne
A stunning antique and vintage 1.68 carat diamond and 14 karat white gold dress ring; part of our diverse diamond jewelry and estate jewelry collections.
This stunning, fine and imp...
Category
Retro Vintage 1950s Engagement Rings
Materials
Diamond, Gold, 14k Gold, White Gold
Mid-Century 1.03 Carats Old Mine Diamond 18 Karat White Gold Engagement Ring
Located in Philadelphia, PA
Three stone ring centers an old mine cut diamond weighing approximately 0.83 carat - K color and SI clarity
Flanked by bar set baguette cut diamonds weighing approximately 0.20 cara...
Category
Retro Vintage 1950s Engagement Rings
Materials
Diamond, White Diamond, Gold, 18k Gold, White Gold
Retro GIA 1.70 Carat Old European Cut Diamond 18 Karat White Gold Ring
Located in Beverly Hills, CA
One Retro GIA 1.70 Carat Old European Cut Diamond 18 Karat White Gold Ring. Featuring one GIA certified 1.70 carat old European cut diamond accompanied with certificate #5221174683 s...
Category
Retro Vintage 1950s Engagement Rings
Materials
Diamond, 18k Gold, White Gold
Read More
Our Guide to Engagement Ring Settings — and How to Choose
There are many ways to showcase a diamond, from traditional prongs to a smooth, streamlined bezel. Here’s everything you need to consider.
Colorful Gemstones Are a Brilliant Choice for Engagement Rings
If diamonds don’t seem right, what about a magnificent sapphire, ruby or emerald?
Our Guide to Fancy-Colored Diamond Engagement Rings
Accounting for just 1 percent of all diamonds, these marvels of nature are exceedingly rare and gorgeously complex.
Our Guide to Victorian, Edwardian and Art Deco Engagement Rings
Learn about these antique jewelry styles, then choose a design that speaks to you.
Talking Diamonds with the Jeweler Behind J. Lo’s Engagement Ring
Alon Ruschin, of Vivid Diamonds & Jewelry, channels his passion for gems into helping clients find just the right ring.
5 Engagement Ring Styles to Consider Right Now
If a classic solitaire isn't for you, explore these alluring alternatives.
The One-of-a-Kind Allure of Custom Engagement Rings
Thinking of going bespoke but not sure what it entails? We ask the experts what you need to know.
Experts Talk Engagement Ring Trends and Shopping Tips
Ready to rock? Some of our favorite jewelry designers and dealers share indispensable advice for choosing that most important ring.