Just purchased a Belt Pulley for one of my 60's.  When I was looking through this gentlemen's inventory we found two that were labeled for 60.  Casting number H-691-A, had normal 10&quot; diameter and 6 1/4&quot; belt face.  The other was also stamped with what looks like H-691 (with no &quot;A&quot;) had a 10' diameter, but had a 5 1/2&quot; belt facing.  It also did not have the two holes tapped for the bolts that would allow you to &quot;press&quot; it off if it became stuck on the shaft.  I do not see it listed in my parts book.  Can anyone solve this small mystery?  Was it an early production pulley referencing the absence of the A suffix?  Does he have something kind of rare?