Hey Joe, I'm not an expert, probably know just enough to be dangerous.
Colt Open Tops are either the Model 1860 Army model or the 1861 Navy model. Both being produced until 1873 when the Peacemaker came out which used cartridges.
The Army models were 44 cal and Navies were 36 cal, so that should help you fiqure out which one you have there.
I know that the Navy model also has a Naval scene on the cylinder.
I have been told that the Army model has a ground battle scene on that cylinder, however, I remember being confused by reading of Naval scenes on the Army model as well, which makes no sense at all.
If you have a 44, maybe you can clear up my confusion and tell me which scene is on the cylinder.
Good Luck