Since the 1950ies, Heathkit produced tube voltmeters. The Heathkit IM-18D is one of these, more from the 60ies, but I do not know the exact production year of my device. Heathkit sold these devices as kits. So you got all parts and soldered it all together. Also calibration was left to the buyer.
You can compare this tube meter with my Heathkit V-7A, which is about 10 years older but very close…
My voltmeter came in a very dirty condition, but it was all optical and after cleaning everything it looks quite well for a device which is about 60 years old.
Inside, the device looked well without any cleaning.
For ohms measurement, a 1.5 volt battery must be inserted. Because this battery leaked in many cases in the past -this is a very well known issue in all heathkit tube meters of that kind- I do not want to insert a battery.
There are two small modifications to replace the battery with a DC voltage source taken from the filament voltage (6.3 volts). One alternative is to use a semiconductor voltage regulator, the other one just uses some resistors and caps. Maybe I will look into this later on.