Charles & all
The bearing race strategy is a new one to me. The + or - and a number such as 1.0 1.5 or in your example 2.0 is a notation to advise how this spindle differs from standard in mm. Not common but they could be ordered with special dimensions, Apollo TBS distributors in the 70's was the source (no one else wanted to carry the inventory), typically it was done for chainline correction.
John Jorgensen
Torrance Ca