That is an impossible question to answer in a few lines or
paragraphs but I will give you a few basic thoughts.
Antique and vintage jewelry to a large degree is valued based on
quality of materials, quality of workmanship, artist or company that
created it, rarity, condition and most important demand.
I have seen early to mid 20th century costume jewelry by famous
designers or manufacturers sell for much more than a mid to late 20th
century piece of gold jewelry sell for. I for one have a hard time
with that but due to the large amount of collectors, the values can
Some styles and time periods have large collector bases and some
have small ones. Demand pushes value higher. Rarity is a factor but
you can have an extremely rare item and if there is no demand it then
has no value but when you put these two together the value rises.
Some time periods or styles are timeless such as Edwardian and Art
Deco styles and these items always have demand.
Of coarse anything created in the upper end of jewelry or pieces
that were once owned by famous people will always have world wide
An important thing to remember is that just because it is Antique
does not mean that it will have lots of value. There are many vintage
items that sell for a fraction of what a new item sells for.
Just a few thoughts that I hope help give you an idea of why some
Vintage jewelry brings high values.