As for JT Powell....here are the only three reference I can find; the 10 ga may be a repeat; one commentator suggested that JT Powell was "John Powell." there are modern English SxS's made in Spain but "regulated in England" carrying the John Powell name but doubt this is connected to the 1800's guns: More searching might turn up something:
-- Question: I have an old side by side double barreled 10 guage shotgun engraved "J. T Powell." Can you tell me anything about it? Both hammers have been broken off; one has been welded back on. Thanks!
Answer: Your shotgun was probably made by John Powell in Great Britain circa 1878-79. Look for the English barrel proofs.
http://www.gabelguns.com/QuestionsAndAnswers/ViewQuestion.asp?QuestionNumber=10844-- 2005: English made 10ga double hammer shotgun in 10ga. with 30" damascus barrels, and with good to fair bores , mostly the area ahead of the chamber has some pitting. The doll's head rib is lightly engraved, as are the side locks, trigger guard, and top tang. LOP is 13 3/4" with a black hard rubber butt-plate.. Splinter style forend has a repaired section on the front left side,where the wood is traditionally very thin, but is a professional job, and not as noticeable.Gun locks up tight, and hammers work good. Chambered for the 3" black powder shell. Barrels have a good damascus pattern.
https://www.gunsamerica.com/965111291/J-T-POWELL-10GA-HAMMER-SHOTGUN.htm-- POWELL 12GAUGE DOUBLE BARREL S/N 1455
Description:
I have a Powell double barrel 12 gauge,30'' barrel 46'' overall serial number 1455. This gun shows its age, dings, scratches, crack in stock. I am selling it for $600OBO.
http://www.gunsinternational.com/guns-fo...un_id=100644344