My thanks to Humber888 for the HP 1740A oscilloscope, and to WaveyDipole for helping transport it to me - I only hope I can repay the favour one day.
I'm hopeful that this unit contains the last part needed to complete a restoration project that's been on the back-burner for the last few years - if so, I'll write it up on the forum in due course. But in the meantime, thanks again to both