Big Blue IBM seemingly since forever is using a fixed numbering scheme for all their parts, where every little thing, dingus and gizmo is labeled with the so-called IBM SKU#. It's always in the form:
digit digit letter digit digit digit digit
For example, SKU# 06H8935 is a "front door bezel with keylock", SKU# 92F0406 is a specific "540MB SCSI hard-drive", and so forth. Just check the detailed listing on this x3650 server. Also, on much older equipment, like a line printer model 2390, a cable carries SKU# 92X2785.
There seems to be a unique number issuing system in place at IBM, as all numbers are unique. Also, they seem to be issued completely random as even some research and listing on my side didn't unearth any patterns or product-category-SKU relations. Obvious is that the letter is used to expand the amount of numbers within the fixed 7 position scheme, by using a Base26 element (didn't check if it's actually all 26 letters). And with IBM being IBM, it could be possible they did a field experiment with humans where they tested which number letter combination could be memorized best with fewest errors. Or there's a check digit/letter hidden somewhere.
I'm unsure if this is more of a superuser.com type question - but I'm posting it here as I think it's more related to computer history. I'm moving it ASAP if comments tell me to. And also, I know that the idea of assuming there's an interesting story behind these SKUs lingers on the side of numerology - but if there is something fascinating to tell, it would be a shame to not bring up the question here, for everyone. Right?