This is a singleton variety and all are known struck on a German silver planchet.  Listed in Riddell's 1845 Monograph as # 462.  One of the more interesting counterfeit CBH varieties.  'UNIM' instead of 'UNUM'.  Rounded bottom to the Shield on the eagle.  Liberty has a relatively small head. Fewer than 10 examples have been documented.
 
This piece has had a rough life. The surfaces aren't great, and it was holed and then plugged. But hey, it is still here, existing, and looking for a loving home.