Looked at a 1925 vintage 12ga Specialty grade today with a vent rib.Rib was wide at the breech as expected but past the rib joint the rib width stepped down to about 3/16" the rest of the way to the muzzle.Is this The original rib? Could not find any pictures showing the top of the vent ribs in any of my books. The barrel is 32". Was not able to get any pictures of it.