I just received a 28 gauge hammer SxS today. It's a gun (lower quality) of French origin with barrels proofed in Belgium. No makers name. I was surprised at the marking of 28-65 within the open oval. So it is designating 2 1/2" chambers. When approximately did 2 3/4" chambers become the standard for the 28 gauge? Reading on the net, an article by Chuck Hawks says all 28 gauge are 2 3/4". That clearly isn't correct.