I've seen 311s with similar chokes in both barrels. Some came like that, others have been reamed.
Try the old dime trick, since these bores usually run close to .729".
With the shotgun proven to be empty, drop a dime in the muzzle. If it doesn't fall through, it's PROBABLY Full. If it squeaks through,it's modified.
Old 311s tend to tightness.Pattern with a good trap load and note the difference in spread, if any.