Hey Dave, did it just to note and here are the numbers:

BB shell width = 68mm
Rear wheels rim offset from bb-shells center: Right side = 7.5mm. Left side = 11mm. Which translates to a 3.5mm difference.

Also feeler gauged the distance(gap) from the tire(25c) to the chainstays(just to note) and they are: Left side = 1.85mm. Right side = 5.08mm. Difference of 3.23mm

Seems like no matter how we measure things (string method, ruler on bb shell to rim, crank arm to chain stays, or bb shell center/rim with tape) that 3mm difference is clearly evident.