Looks to be proofed for powder T prior to 1923. I can't tell from any of the photos if it is a monobloc or not! 19.2 is ten gauge bore, real as a heart attack.
What an awesome piece for putting 1 1/4 oz of hard 5s on a scampering rooster at 35-40 yards or so.
Wish it fit me. Wish I owned it, if that were the case.

Best,
Ted