A Tektronix engineer visiting IBM in the early 1960s saw that they were developing an oscilloscope. When he inquired about it, he was told that IBM wanted a scope for their field-service engineers. After some (probably brief!) internal discussions back in Oregon, Tektronix offered to develop a portable scope to IBM's specifications. IBM had two requirements: it had to be fast enough for computer work (where "computer" probably means System/360) and it had to fit under an airline seat. To satisfy these requirements, Tektronix produced the twenty-nine-pound 50-MHz 453. If you buy one today, many of them still say "Property of IBM".
After Jim told me this story, I needed to see for myself. So one time that I was in California at the De Anza Flea Market, I bought a ten-dollar 453 (serial number 23,109), and proceeded to use it as my carry-on for my flight back to Boston. And, yes, it does fit under an airline seat. Here's the proof:
When I sent this picture to Jim, here's the letter he sent in return:
Here's the text:
Ah, yes. The Tek 453.
I had a 453 in building 20 (serial number 7402) that I used for years; it was stone reliable. When I wasn't using it, I studied it. Early 453s had nuvistor triodes at the attenuator output and in the trigger buffers---later versions (serial numbers 20,000 and up) used FETs because it took a while for FETs to be good enough for Tek standards. In about 1966 Carl Battjes figured out a way to use T-coil bandwidth boosting with transistors, which, of course, everybody knew was impossible. He applied T-coils to the 50-MHz 453, tripled the bandwidth, and begat the 454, which had an astonishing 150-MHz bandwidth. But the 453 was the beginning...
If you need any 453 parts, let me know. I have plenty.
Finally, I would like to thank the TSA agents at San Francisco International Airport for their cool professionalism. They didn't freak out all at when I put the 453 into the X-ray machine. You would think that a middle-aged guy carrying a middle-aged scope was a normal occurrence! (They did swab it for explosive residue, but I was expecting a much more invasive search.)