Oh, it can Stan.
The effective constriction of a screw in choke is very much affected by the length of the choke 'throat'.
It acts as a jug section, and depending on it's length and diameter can essentially redefine the barrel ID.
'Cylinder' screw in chokes generally do not throw a true cylinder pattern, and 'most' screw in chokes throw tighter than marked.
One exception I've seen to that rule is Krieghoff, where the choke leade returns to barrel I.D. in a very short distance. At least it does in my K-20.
If that 'IC' has a measurable section at .630 in front of it, it could very well print IC.
