Can't help with the first one but Jana International was an importer, now defunct. The 1851 was generally called the "Navy model". It has an octagon barrel and was originally produced in .36 caliber only but many replicas were produced in .44 caliber, if we can call it a "replica" of a gun with no "original". The Army model Colt was the .44 caliber model of 1860. It has the round, sort of streamlined looking barrel and the rack & pinnon loading lever.