Above you say "Although these replicas are old enough and good enough to have passed as originals before, I'm not like that." And yet, now that you're selling it, you're EXACTLY like that. You imply it's real, and say you never contacted Colt about it. But you did and they told you it was a...
As you have learned, that is not a Colt SAA. It is a copy of a Colt, made in Mexico. They were quite common in the 1800s, and there are several key features that point to this fact. As such, it's worth very little. Even if in excellent condition, they only sell for a few hundred dollars...