[FONT=Helvetica Neue, Helvetica, ヒラギノ角ゴ Pro W3, Hiragino Kaku Gothic Pro, メイリオ, Meiryo, MS Pゴシック, arial, sans-serif]I ran across this description off a site, not sure if your able to get the maker of the back-RARE EARLY 1800's 1 PIECE U.S. NAVAL NAVY BUTTON by I. MOORE & CO. Very nice save, congrats.[/FONT]
You can search Tnets older posts for cleaning techniques. There are tons of them, mine can get pretty aggressive, that's not for everyone.
The least you can try are a soapy bath and toothbrush cleaning. I also have an ultrasonic cleaner, they really work to get every bit of dirt out of every nook and cranny, but then your pc. may feel rough to the touch. a little paste wax to preserve the metal will smooth it back out again.
You can get the US cleaners pretty inexpensively online, and I use mine all the time on finds, so it's worth it. They will not remove corrosion however, just the dirt.
Anything more than that can be aggressive...