Sixth-plate tintype, behind mat and cover glass in half of a case. Two ships photographed in harbor; the style looks like US Civil War ships, and the time period (circa 1863) also fits.
Behind the case is a slip of paper with the name John C. Sweeney. Possibly served onboard.
Some flaking to the image, but it all appears very stable and should stay exactly as-is if not taken apart and handled.