What did you mean by "I preffered my TI SR-50" in post #8?
To achieve better efficiency in their LED drive, hp charged tiny inductors with bipolar xitters, then let them discharge into the LEDs.
MOSTEK talked hp into selling the 35s through mail order.
One guy who didn't receive a free 35, scrounged some chips and built his own 45 in a metal case and full size keys. Ugly, but it worked. The 35 used 3 256 word ROMs in TO-5 cans, the 45 used a 1024 word ROM on a single chip. I think.
After he 35 was introduced one of the slide rule companies came to visit. Their marketing manager pull a 35 out of his pocket and said, "We want one of those". Had to turn him down.
Another fellow came in with a design based on an analog computer. Had drawings pinned to the wall all around the conference room. Said it had to run a 1MZ clock rate. hp clock was 200KHZ. Had to turn him down too.
hp didn't even consider TI because they feared they would be a competitor. They visited MOSTEK and at the end of the meeting, said "when can you start". Very few legalities.
Don't mess with B+!
(Signal Corps. Motto)
New ones are 9-pin miniature tubes.
If you have one with a 4-digit SN#.......
My 200CD from 1961 is S/N 109-31487. So that is a fairly high number.
However, the 200CDs in the picture at my website below could have been low numbers. These or at least one would have been bought late 1953. See photo P21 on this page http://www.beta-aa.com/misc_photos.html
I believe the scope in the photo was a DuMont, and the voltmeters HP 400H.
Also before 1955 HP brought out their first oscilloscope.
I still have my trusty 41CV that got me through engineering school in the 80's. We don' need no steenking equals sign!