Aside from the scopes with CRTs, maybe an electrometer? I think that some older types used a tube front end for extra high impedance.
No, the scopes are the obvious ones, so they're not the answer. I don't have an electrometer, there's one of the instruments that incorporates at least one tube - I guess one can only tell it if one knows and recognizes the instrument
There's a higher resolution picture:
But you won't be able to read the instruments numbers, googleing them all would be too easy ...