This small (15.5”) but heavy (18 lbs) bronze and steel breechloading cannon model, unidentified until today, was demonstrated before President Lincoln and his cabinet in the White House in 1861. The primary inventor and promoter of this cannon design was Walter G. Sherwin of Cincinnati, OH. For further information you can follow these links.
The Story: https://books.google.com/books?id=1RkkDwAAQBAJ&lpg=PT171&ots=D1wXEblpf5&dq=w.g.%20sherwin%20cincinnati&pg=PT169#v=onepage&q=w.g.%20sherwin%20cincinnati&f=false
The Auction: https://www.cowanauctions.com/lot/unidentified-patent-model-3908401
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