HP-41 Manuals and Quick Reference Card Revisions

[vervalin]

Ok, I've pondered this for quite some time and now I will ask the community.

I have lots and lots of HP-41 manuals and Quick Reference cards for 41CV, 41CX, Printer, Card Reader, etc.

Often these have a revision like Rev D or Rev A, etc printed on the back or inside the front cover.

So, like on some of the Quick Reference cards one will be Rev B and another Rev D but they are IDENTICAL in every way possible. So, the question is WHY? Why the different revisions? Are they just "different" printings?

Thanks!!