If the barrel had came with screw in chokes it would be marked so on the barrel.
I know basically nothing about Remington 1187 shotguns...could someone have put an older 1100 barrel made prior to screw on the gun ?
A good gunsmith should be able to tell what chokes you have....gunsmiths around here used to put thin wall Colonial chokes....there were a few makers besides Briley.
