You are correct Miller, for 12g. To be clear, I measured the bore and constriction using a Stan Baker gauge to which I affixed a fabric tape measure.
About 2008 I issued a request on the 16g site for 16g choke measurements and a number of respondents provided data for Parker, Fox, Baker, Ithaca, and Smith guns. Almost all had a choke length of 1 1/2 to 2 inches with a very short parallel section at the muzzle.
The pre-1913 16g Smiths that I have owned; 1911 OOE, 1906 2E, 1906 OE, all had about 1 1/2" choke lengths.
16g Parker guns made from 1891 to 1927 with chokes from .002 to .040 all had a choke length of 1 1/2" to 2". I think Dave Miles and Austin Hogan provided the data.
Fox 16g doubles made in 28', 33', and 37' (? measured by Dave Noreen) were found to have chokes about 3 1/2 inches long in the tighter choked barrels BUT a 1936' 32-inch barrel A-grade had full chokes of only 2 1/2 inches.
