In my opinion: it has historical value to a museum, particularly those which focus on issues local to Iowa, or one dedicated to William McKinley. Due to the condition, and not widely applicable subject matter, its monetary value is somewhere in the neighborhood of $10 -- its current going rate on the consumer market. If it were me: I would see if I could donate it to the Audubon Public Library, and get my name added as a donor of cultural resources to an exhibit at the library. That little feather in one's cap is probably far more valuable than the eBay price of this piece, or any pleasure one might derive from having it in a personal collection (unless you intend to start collecting either funerary artifacts or start a William McKinley shrine).
If that sort of thing interests you, I would advise you not to donate this to the Iowa State Historical Society (which has its museum in Des Moines). It would almost certainly not get displayed, and they do not guarantee that they will not throw away donations immediately upon receiving them. You would likely never know if it got put in a storage stack or went in the recycling. The community this piece is relevant to, I am sure, would appreciate it far more.
Just my opinion. For what it's worth, I was not able to locate another copy of this piece. So there is that. The unfortunate part is the condition.
-mcl
