I assume this is what you're talking about?
http://books.google.com/books?id=cU...ge&q&f=false"Thickness" is probably as thin as can be possible and still live up to the "sterling silver" claim. According to the above ad (from 1980) the silver content is said to be made "by impressing a finely rolled sheet of sterling silver between two matching minting dies." With that sort of claim, you'd probably need dozens (if not hundreds) of them to make up anything near an ounce of silver, so value is next to nothing, at least as far as the claim of silver content is concerned.
Same thing can be said for gold replicas, too, which were also popular in that day.