Thank you rigbymauser and grandveneur!

Mike - I agree no earlier than 1895 based on Watson address.

Lastly, an abbreviated range report - I was out at range today to test a .361" 145gr LRN load for a single Alex Henry takedown falling block, also in 360EX. I tried that load in the Watson...not a good fit. I also tried 3 rounds I'd loaded earlier using heavier jacked .358" 185gr JHP. Same powder charge. This heavier load with jacketed bullets was much better. More testing ahead. And slugging the bore.