Per your request for a reliable ID - My 1963 Navy Arms catalog named this gun the "REB Revolver ... beautiful, faithful reproduction of the Confederate Griswald & Grier, based on the 1851 action." Back then it sold for $89.95
@OLUT has identified the revolver. It is the Navy Arms revolver, the "REB" revolver. A beautiful, if not entirely faithful, intended to be, reproduction of the Griswold and Grier revolver. That has the stepped cylinder. That implies that the caliber is 44. All of the Griswold and Grier revolvers were 36 caliber.