[Researcher]

This is interesting if correct; 2 1/2" 12g shells in 1927?? Unfortunately, neither the box label nor an individual shell are shown.
http://www.gunauction.com/buy/7595905

I suspect the person who wrote the copy measured the length of the loaded shell. From this page in the 1926 Edw. K. Tryon Company catalogue states the 12-gauge AJAX HEAVIES come in a 2 3/4 inch case.



The box on this catalogue page has the Lowell, Mass. address rather than the New York, NY on the box in the auction.