Help with a 1859 Sharps & Hankins Navy Carbine

Hello,

I am being offered a model 1859 Sharps and Hankins Navy Carbine, the seller describes it as .52 caliber rimfire and still having the leather wrap around the barrel, although in poor condition. I should have pictures of it soon (today) and in the meantime I was hoping you could tell me what to look for in general, in case he doesn't send the photos before I go to meet with him later today. I have no experience with weapons of this era, so any education on it is welcome.

Thanks in advance.