Actually I think it was the British, but can't put an actual parson/Company or date on it. It was as the name implied an "Improved Cylinder, meant to give nearly the spread of a cylinder bore but elimanate the problems associated with a true cylinder with the older shells. The IC as originated had a constriction of .005"-.006".

Americans for the most part did bore their bbls to Ľ choke, but stamped them IC. I think that extremely few true IC bbls have been bored in the US.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra