Super find! I think the patent is for something called a "Photographic Medal". It might have held a photo of General McClellan in it. Here is a similar one that sold on eBay-
http://cgi.ebay.com/ws/eBayISAPI.dl...FsdbbT6iN5w%3D&viewitem=&orig_cvip=true&rt=nc
McClellan & Pendleton Ferrotype Medallion - 1864
When my father was alive, he collected coins from circulation. So did his father; passing along his collection. Occasionally they would find items that were not coins in the pile of change. Here is an 1864 back to back McClellan & Pendleton Ferrotype Medallion. This scarce, slightly smaller-size, 22 mm (.87 inch), reeded edge ferro is in very good condition. A 12 mm (.47 in) ferrotype of “m’clellan” is framed by "union. constitution. laws. and flag". The ferrotype of “pendleton” is framed by” p=t.apr 2. 1861” with 13 stars. A 1.5 mm (.06 in) hole is positioned between flag and union.
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