Tube opamp? How about dual opamps?
Here are photos of a tube unit including an analog multiplier, phase discriminator and a relay control driver (a big relay was inserted in a socket near two potentiometers on the left). Used in ground control gear (don't ask me - control of what..., all I know it's ground, not mobile, piece). Chassis is machined of a solid aluminum piece - 31*12*5 cm. There's a total of nine miniature tubes (2 RF pentodes, 7 dual triodes). The compartments on the left, top right and bottom right are normally covered with tin lids, so the whole unit is one smooth brick with a window in it. These units are stacked vertically in a rack, windows form a chimney for air cooling. The thing ran on a low B+ - all caps are 160V rated, the largest resistors 1W rated. Note the daisy-chained heater bus (white-blue wires) - something you don't want in an audio circuit...
