Mr. Houchin's book on page 300 implies that the long range wild fowl guns had 3 marking 1. The words Long Range or wildfowl. (Mine has this.) 2. The 3" chamber stamp (not on mine) and 3. The L sometimes on the water table. Mine doesn't have it.
I measured the chambers and they are 2 3/4". Is Hochin's book wrong?