I would indeed test that but I am stuck with a ~10nS rise time output here. I suppose it's a good excuse to build a Jim Williams pulse generator...
I must admit when I cracked it open, the timebase did leave me a bit "whaaat?" in this case because the board wobbles when you turn the knob. I will probably leave it be for now and just buy another 1740A to keep in the cupboard just in case
However looking at this, it's museum grade inside. The cal seals were still present from '84. The only thing showing any wear or damage is the feet and I don't think I've ever seen scope feet that aren't knackered. It'll get some makeshift ones from whatever I can find on RS.
Alas no 485 has ever come my way for a price I'd pay or I'd snap it up instantly
... still slightly regretting selling my 475 which was in mint condition a couple of years ago. That was second best to the 485.