In his book The Complete Guide to Buffalo Nickels, David W. Lange observed of this issue, "If someone has not had the opportunity to examine Type 1 proofs, these may easily be confused with very well struck currency pieces." Indeed, distinguishing the two is not dependent on strike alone. The proofs have an extremely fine crystalline or satin finish that is quite different from conventional mint luster, but this quality may be obscured on pieces that have been harshly cleaned.  Collectors of the time noted the minimal differences unfavorably, yet this issue still enjoyed respectable sales for the novelty of its design. They've suffered an unusually high attrition rate, and it's possible that many were later spent intentionally or accidentally. Gems are quite elusive and are also in much demand as the only Type 1 issue.