They are known as "Bryan Dollars." They were made of coin silver (90% silver, 10% copper). The idea was that a silver dollar really needed to be their size in order to be worth a dollar. A government dollar weighed 412 1/2 grains. These pieces weighed 823 grains or something close to it depending upon the time it was issued. The idea was that Bryan's "free silver" position was going to result in massive inflation. The three principle issuers of these pieces were the Gorham Silversmiths (most common), the Tiffany Jewelry Stores (all scarce) and the Spaulding Jewelry Company (quite scarce, but not as popular as Tiffany) which was located in Chicago.
