Good points on the engraving Dave. You Do see details!!
In the description, it says bore at muzzle somewhat tapered or flared, or words to that effect, to make for easier loading.
It may Help in loading, but the idea was to offer some relief in the bore to reduce pressure, ensuring a superior pattern at longer range.
I recall W'm Keith Neil killing a wood-pigeon with a long barreled fowling piece as it flew out of a tree at 76 yards. Something hard to accomplish with a modern shotgun.
Best,
R.