Colt resumed making them (1970s?) because there was no law against cloning them back then and several companies were doing so and making money. Colt, when they too decided to make money off the black powder market started their serial #s right where the older ones left off. This really complicated things for collectors as a little burnishing or pitting of a critical number makes it really hard to tell an original from a 20th or a 21st century version. The good news is the old dies have by now completely worn out. Indeed there are books out there on telling the old ones from the Fabulous Fakes (can't really call the newer Colt versions Clones or fakes, as they really are Colts). There are subtle variations in the engravings, spectro analysis of the steels compositions will also reveal difference in the steels, etc. Then there is the issue of who actually makes which components, etc. Colt started using sub contractors for many parts way back in the WWI days and never really got out of the habit. Heck, they even had complete pistols made by competitors shipped to them just so they could stamp their name on it and sell it as a Colt, i.e., the 380 Pony (made by Astra). Buying or validating an actual authentic Civil War period pistol is an act that (should and often does) involve a lot of research. Just don't get too excited by a number is what is what I'm saying.