Take it to a gunsmith and ask him to measure it. He probably won't even charge you for something this simple. If you have a lot of shotguns to check, you can buy a gauge from him.
If a dime does not fit down the end of the barral it was full choke. If it is a modified choke a dime will fit inside. Just my 2 cents
A barrel with a full choke.
Either a full choke,or extra full choke shotgun barrel.
With standard chokes, Full Choke is the tightest. However, there are non-standard chokes for SOME shotguns (used by turkey hunters) that are Extra Full Choke.
ABOUT .660 IN A 12 GA SHOTGUN, TIGHEST NORMAL CHOKE EXCEPT FOR NEW TURKEY GUNS.
Cylinder to Full depending on what discipline you are into.
Refers to the amount of constriction at the muzzle.