I just meant that an E bb has less axle protruding on the drive side so as to preserve the chainline as the bb fits outside the fm mounting plate. So a desperate owner could fit a 68mm E bb to a 73mm bb shell to get the chainline right(ish). Not much of a solution though because (a) the non-driveside adapter wouldn't tighten up the bb and (b) the non-drive side would be shifted to the right which could make it tight for clearance against the chainstay.
It actually sounds more likely that the RM bb shell is a 68 and so the spacer was there to stop the bb being too big for the shell (as the fm mounting plate is absent). I don't know what you mean by a collar though, I haven't seen anything like that. Maybe in tightening up the adaptor against this collar you can foul the axle somehow and it won't turn?
Hey don't knock it - maybe the fact that the bb wouldn't turn persuaded the owner to give the frame away?!?
K, just checked the BB and it is indeed 68mm and it's smooth. the frame BB shell is also 68mm. i think it was either cuz it was cold, as it was sitting outside for a while in freezing weather when i was playing with it, or the cups might have been over-tightened a little bit too much.
if you look at the third pic of the bb, there's gold colour collar/ring on the axle itself inside the BB cup that i've not seen before. i'm guessing it's for the E-plate or whatever.
the prev owner gave me the frame as he knew i really wanted it, regardless of the dents. it had nothing to do with the bb, as it wasn't seized in the frame and was removed easily enough. he is a very generous person and i have nothing but praise for the guy.
anyway, i've sent you an PM regarding the BB so if you want it, let me know.