There were about 45000 NIDs produced, with 415 being 28-gauges. So, 28-gauge production was .9%. The Flues 28-gauge was introduced in 1912. Flues serial numbers from 1912 through the end covered 181865, but that serial number run included some NIG & Two-Bolt hammer guns and the Flues Single Barrel Trap Guns. So, would 175000 be reasonable? .9% of 175000 = 1575.
Thank you Researcher. Your reasoning sounds valid to me. I guess your original answer is probably the most likely correct, unless Walt Snyder happens to have the actual number in hand...Geo