Yep, you've crossed the 1978 CPSC induced chasm caused by the mandate against the dangerous flat cage derailleurs to the lipped models. I believe the CR site has a snippet provided by one of the list members on this topic. The +1.5 marking indicates the longer post '78 spindle but apparently wasn't kept on the spindles too long.
Charlie Young
Honeybrook, PA
> I used to know this, but have forgotten how it goes. Some time in the
late
> 70s to early 80s Campy changed the arrangement of their cranks and BBs ,
so
> that newer cranks do not line up well on older BBs and vice versa. Does
> anyone know the rules on that? I took a 175 crank (2 in a circle, 1982?)
off
> a bike with a 70-SS spindle and put on a 170 (7 in a diamond, 1977?) and
the
> chain line was outboard about 2-3 mm from previously. And in a separate
> case, I found a BB that has +1 68SS +1.5 on it. Anyone know what that
means?
> Please reply directly as well as to the list as I don't always get all
the
> postings.
>
> Thanks!
> Bob Freeman