These cabochons were manufactured in West Germany from the 1950's - 1970's for the costume jewelry trade. They show typical wear for glass of this age -- such as foil flaking or small nicks around the edges -- but it does not detract from their beauty or elegance.
I use these pieces in my own work which you can view at my other Etsy shop: http://beadmask.etsy.com
As you can see, I typically set them in seed beaded bezels, vintage filigrees or leather. They are also excellent for mounting, gluing, wrapping, altered art and whatever else your imagination can stir up!