Same PN, different 18" 9 spoke mags

[Julio]

A few years ago I picked up an 18" 9 spoke mag that came on one of the late '70s Sporties for my '96 XL1200S. 
Different axle spacers and a 5/16" pulley spacer and she bolted right up.
I just picked up another one for my '85 FXST and lo and behold, it has different offsets than the first one. Both wheels have the AMF PN40995-78 casting, yet the hubs are different.
I Googled the PN and up comes the same mag on E-Bay, but for a drum brake.
All three wheels have the same number from AMF, yet they're different.
Anyone know why? 

[hdbikedoc]

coulds be a xlcr and a xl had a different offset don't have a parts book at home but that could be the differents, sometime you would order a part number and the part would be stamped with a different number it was the amf days