As was stated above, there simply wasn't enough market demand for 28-gauge guns to make it worthwhile for the A.H. Fox Gun Co. to add one to their offerings. There were very few A.H. Fox Gun Co. ads that even mentioned what gauges their guns were offered in and even less that actually touted their 16- and 20-gauge guns like this one from May 26, 1912 --
By the time the Spanish-American war was winding down, the Brothers P knew two things -- (1) The great bulk of North American shooters owned one gun, a 12-gauge, and that the repeater was what most new shooters were going to buy; and (2) therefore, their real client base for their upscale product were the existing Parker shooters. So, they needed to entice them with something new and novel. Parker Bros. entered the 28-gauge market by taking a bunch of 0-frame 20-gauge guns that had been languishing in inventory and rebarreling them to 28-gauge, and telling their clients these are just the ticket for Quail or even Ducks at some of the California Duck Clubs. At that time North American 28-gauge factory shells were put up in a 2 1/2 inch case carrying a load of 1 3/4 drams of bulk smokeless powder pushing 5/8 ounce of shot. Our ammo manufacturers did also offer 2 7/8 inch NPEs and gun cranks like Chas. Askins were stuffing these with 2 1/8 drams of powder and 3/4 ounce of shot. Askins had a 30-inch barrel Parker Bros. 28-gauge that weighed 6 3/4 pounds!! Western Cartridge Co. didn't introduced their 28-gauge progressive burning smokeless powder Super-X load until 1932. Ithaca Gun Co. dropped the 28-gauge from their catalogues with the introduction of the NID in 1926, but at that time Ithaca did return to cataloging a 28-gauge gun,
and a few smallbore Fox doubles were known to escape Utica with an extra set of unchambered 20-gauge barrels with a 28-gauge rim cut.