Jim I don't recognise the mark but I think it could be a Belgian Centaure. The reason I say that is because Centaure is the only repro I know of that has a straight stepped cylinder like the original Colt 1860 Army. Most repros have a slightly diagonal angle where the cylinder steps up but on a Centaure it's a straight 90 degree angle.
Even if this gun is a Centaure I think $450 is too high. Centaure's are not common but the bad defarb job ruins most of the Centaure collectibility and value for me. At $200 it would be a good deal for parts if I was 100% sure it was a Centaure, which I am not.