I am surprised at the results as Mint officials were adamant about the fineness of medals. To have used other than 900/1000 or pure metal would have caused serious accounting problems for the bullion.

Two possibilities come to mind. The first is that the dies were used outside the Mint, perhaps by Peter Krider, for special runs of such medals. The other is that a Mint official brought in his own silver (of a lesser fineness) for a special striking. The latter issues would not have been sold to the public by the Mint, however.

There is no hint in the archives about these lower finenesses.