Keystone Arms Co was a trade name used by E.K. Tryon Jr. & Co, a large catalog hardware store in Philadelphia. The gun would have been made during the early 1900's through WW2, and could have been made by any of a number of manufacturers. That serial number leads one to think H&R.
Not sure but I have #9972
No known sn data published.
16 gauge arm shotgun made in palmetto c. o. Philadelphia Pa
A shotgun barrel with a cylinder bore choke.
yes a rifled shotgun barrel or smooth shotgun barrel
Buy Shotgun. Buy Shotgun.
Barrel, stock,
when did the make the smithsonian double barrel shotgun
What is the value of a Beebe arms double barrel shotgun?
One difference is that the inside of a shotgun barrel is smooth and the inside of a rifle barrel is what they call "fluted" which puts rotation on the bullet as it moves though the barrel.
I do not personally, but yes, there is a single shot rifle that can have the rifle barrel replaced with a shotgun barrel.
Yes, you can remove the barrel of a model 66 Shotgun!