Regarding Skeet II choke and where it falls on the spectrum- both camps are correct. Up to the 1950s or early 60s many skeet guns had Skeet constrictions between .000" and .004" with Skeet II around .008". Now, just how often this was the actual case is open to conjecture as today's tolerance for a given constriction falls in the +/-.003" range. That would make it very possible for the Skeet choke to be tighter than Skeet II in some cases. In fact, I have seen several Winchester Model 21 skeet guns with the left barrel more open than the right which was passed off as the purchaser's preference. That may be so but would need to see documentation to believe that.
Later, there was less negative stigma toward breaking targets past the center mark and the desire for a tighter choke came into being. As few guns had Skeet II and those who did have that constriction often had little idea what it was, the Skeet II designation was moved between IC and Mod. This I have seen in ads for Poly-choke devices from the early 70s and with the early Winchoke system which came into being in the 60s if I remember correctly.
This is how I see this conundrum based on my sources and memory. Depending on the era one references (including modern choke manufacturers and not just us here) Skeet II could be on either side of IC. General opinion currently has Skeet II on the tight side of IC but that is not written in stone.
