121mm is most likely the length for a the standard crankset, which is sort of long for a single-ringed crankset.

http://www.bikeforums.net/showthread...ino-maxy-crank
Quick search of BF shows your Maxy COULD be ISO taper, which is the more Italian standard of tapers.

Do you have pictures of the your set of Maxy? I'd do a quick search on Velobase to see what shows up on there.