I have miked a bunch of bores and long ago came to the conclusion that there is no such thing as a factory style of choking. Pick a manufacturer and you will find a mix of tapers and parallels (and bells). I think that this kind of stuff will happen as long as the chokes are hand reamed. If the bores were being reamed for a pattern and not a constriction, it stands to reason that there would be more fiddling going on.
As previously noted, the Lefever the bores are parallel, not tapered. The only Lefevers I have have miked were fairly open and the chokes were quite short, so I can't speak to the long taper aspect. Winchester seems to get a tighter pattern with less constriction than the others. This is very subjective, but the Winchester barrels seem to have a better finish than the rest. Like the others, Ithaca chokes are a mix of profiles but generally deliver good to outstanding patterns.
