Is there any difference in the length of the barrels? Prior to the invention of screw in chokes,the most common method of changing chokes was to change barrels.
30 inch barrels were commonly full choke
28 inch barrels were commonly modified choke
26 inch barrels were commonly improved cylinder choke
Most serious shotgunners had at least two barrels for their shotgun.
Or they had a gun for each barrel.
The choke should be stamped on the barrel near the receiver, Full, Mod or Imp Cyl, unless this has worn off. Some stampings were more defined than others.