I ask that, because on other makes, prior to, or right at WW2, 2 5/8's was very often the rpesumed STANDARD in 12 gauges, and it was 2 3/4's guns that were specifically marked.
Note too what I said about measuring. My Galazan gauge DEFINITELY does not sit as deeply on this gun as it does on other [more modern] 2 3/4 guns I own. And that really has me suspicious.