Im pretty sure itll work on a No1. I had a 577Nitro built on a No.1 by JD Jones.

More and more, Im thinking a T/C Encore would be cool. I know its not classic and that is bothersome; but it seems the easiest--IF (big IF) I can find a suitable barrel groove and twist.

I had planned to build it on a Greener Martini action and thats still a possibility but a T/C seems like its better for everything besides classic looks