https://www.collectorsfirearms.com/p...navy-ac18.html
About the closest I could find for a comparison. Having the revolver in hand would make comparisons easier. Attention to detail, like checkering on hammer, font as was mentioned before. If all checks out, then take it to a person who knows and specializes in old Colts. I had an original Smith that went to an expert and I was pleasantly surprised with the outcome.