A bit of Ithaca 28-gauge history. With the introduction of the NID in 1926, Ithaca added the .410-bore to their catalog offerings and dropped the 28-gauge.
1926 Ithaca Gun Co. catalog pg 3.jpg
1926 Ithaca Gun Co. catalog Specifications.jpg
That remained the case through 1931.
1931 Ithaca Gun Co. Catalog specifications.jpg
Western Cartridge Co. introduced the progressive burning smokeless powder, high velocity, 3/4-ounce, 28-gauge load in their March 1, 1931,
Western Ammunition for Rifle, Revolver and Shotgun.
Super-X Loads, March 1, 1931.jpg
The specifications in the first 1932 Ithaca Gun Co. catalog includes the 28-gauge.
1932 Ithaca Gun Co. Catalog pg 3.jpg
1932 Ithaca Gun Co. Catalog specifications.jpg
Ithaca Gun Co ad from the April 1932 issue of
Field & Stream.
NID 28-ga Field & Stream April 1932.jpg
All the above said, Ithaca did make and ship 28-gauge NIDs during the 1926 to 31 period. Walter lettered my No. 2 28-gauge with a serial number in the 431xxx range as shipped 03/29/27.