My thought was, because people with old polygraphs in my experience want to dump them, while people with an oscilloscope of the same capabilities want a premium for them.
One guy near where I live has an uncle who collected stuff, and he has an old Heathkit oscilloscope he'd like $75 for. Square tube, relatively massive body, very, very low bandwidth. He also wants about $50 for the old tube base done, with the round CRT display. And it won't show a trace when powered up.
But he has a somewhat dinged up polygraph with chart recorder that is for about $10.
Could I, perhaps with some modifications, turn that polygraph into what works as a low-bandwidth oscilloscope/oscillograph? The old tube based one would be of collection interest only, and being old and Heathkit, I doubt their accuracy. Is there any way the old polygraph could be turned into the world's least practical oscilloscope?