On Tue, 6 Jun 2023, Sellam Abraham via cctalk wrote:
The primary distinguishing features of the very first run of 5150's are:
1) No "B" inside a circle stamped on the back panel
2) Only two case screws on lower right and left of back panel (none on top)
3) Black power supply
Here's a photo that shows this ==>
https://www.minuszerodegrees.net/5150/early/5150_early_case_rear.jpg
Bill Degnan (from whom I learned all this) knows more about this.
I will have to check for the 'B', but there are a few cubic meters of
stuff to move to get to it.
2 case screws
power supply was not only black, but had a white switch, instead of the
red paddle.
in addition to the round plugged hole, it might also have originally had a
"D hole" for a DB25. When I mentioned such to my department chairman (an
unusually competent fellow), he used department money to buy a Greenlee
chassis punch, so we added those DB25 mounts to a few others as needed,
instead of tying up a slot just for a bracket.
