Learning about Vintage Jewelry

I sell costume jewelry, mostly new. But I recently discovered vintage jewelery, and I am now collecting, wearing, and selling. It is so interesting, and I like doing the research. My current process is to purchase anything with a mark. Seriously - I cannot read most of the marks even with my glasses on, so as long as it has a mark, I buy it. I bring home and use a magnifying glass and / or my son to find out exactly what is stamped / marked on it. Makes it fun, when you get home and find a KJL (Kenneth J Lane) stamp on a Brooch set. I also like to find marks from designers I have never heard of and then do the research. There are a few good sites out there for just this purpose. I will list of the links in case you are interested.