These digital battery powered multimeters by Beckman Industrial Corp. in USA. They have a clear digital readout on a LCD screen and will measure AC and DC voltage and current as well as resistance and conductance. Function and range adjustment is accomplished via a single switch. The instruments are powered by a 9 Volt PP3 size battery.
The Taylor Model 128 Multimeter also known as a Post Office Meter Multirange 12C/1 is almost identical to the model 72"
when measuring 1000Ω standard resistor on 1kΩ range
The model HD100 was given to me by Barry Carter who said he
was fed up
with it falling out of a cupboard whenever he went to look for
something! Unfortunately the LCD screen was damaged and there was a
in the circuitry which caused what could be seen of the readout to stay
at 1998. I have now disposed of this one and acquired a model HD110
which is similar.
Internal construction of HD100
How much is it worth? Instruments such as this are of little use today and not many people seem interested in them. Expect to pay £5-£10.