When Gallery Mint was making reproduction coins, we had a sample board of all the denominations as a reference so we knew the specs when making blanks. This piece is obviously from that board since the flip has the pinhole where it was pinned to the board. The original coins were struck sans collar and would grow larger when struck, so we had to do a little reverse engineering so the finished piece would be the same size as the original coins. 
 
.8924 silver