[Closed] Buying 2nd hand / antique jewlery

Now I know that walking into Lizzie Dukes or H Samuel etc everythings expensive, shiny, and overpriced.

But there's a few boutique/retro/antique/bohemian jewlers arround here and I saw something in the window the other day and though it looked very much like something the missus might wear. Turned out to have a 65th wedding aniversary inscription onthe back so decided against it.

I've now got a magpie like facination with their window displays, any way of valueing it? Or just accept that the shop owner probably picked it up for a fiver at a car boot and is making a living?