Still some mysteries here. The R on the barrels, forward of the flats, does appear to have a crown along with it--which to me makes it more likely an indication of reproof. However, the sources I have indicate that the R for reproof didn't come into use until the Rules of 1925. And if that gun were proofed post-1925, then it would have some additional proofmarks it doesn't have.
Re choke on the L flat, not on the right: Does not necessarily mean cylinder, but it does mean very little choke. But it could be as much as .007 and still not be marked choke. .008 or more, had to be marked choke.
