Pretty cool. If that's the fort I think it is, you should be able to find native American, revolutionary war, and early settlers relics. Very nice area to hunt. Can't wait to see what else you find! Congratulations!
The large two-slot object in the upper center of the photo is a variety of "buckle-shield" invented and patented in 1879 by David Mosman of New Britain, CT. See the photos, US Patent information, and advertizement below. Patented on Dec. 16, 1879, and marked with that date. Ones manufactured after the Patent expired (17 years) are not marked.