This is a relatively low-grade, circulated example of this scarce 1891 Z1-B variety. This could mean this piece stayed in circulation a while or became someones pocket-piece. This example is the lightest (2.46 grams) and thinnest (1.17 mm) example I've yet measured, and undoubtably its advanced wear is a factor.
 
I don't get counterfeit IHCs in my inventory very often, and when I do they usually sell quickly. This example should fill a nice type hole in your collection.