Judd 1756 is an aluminum version of a regular-issue 1885 $20. These are often called "die trials" which implies a test to see how the details of the coin would strike up. Rather, these are most likely coins that were made as curiosities for sale to collectors. According to Saul Teichman of uspatterns.com, these were most likely produced and sold as complete sets of different denominations in aluminum. Based on the known survivors of each denomination, it is doubtful if the Mint produced more than two sets.
Only two examples are known of Judd 1756 - one in PCGS PR65CAM and a second in PCGS PR66.