This is a more accurate and virtually identical meter to the earlier model 71. The 1Amp fuse has been omitted and a 2.5 kV socket has been added but otherwise is much the same.
Unfortunately the meter movement was found
to be open circuit but as I also have a model 71
with a good meter but several faulty and or open circuit
resistors I have
exchanged the meter and scaleplates to get a working instrument.
What does TTR stand for?
When Thorn bought Radio Rentals in 1968,
the two businesses were merged to form Thorn Television Rentals.
The Taylor model 128 is almost
identical except it does not have the 2.5Amp or 2500 V ranges
You will find more information
here about these instruments and other similar models. AVO produced a range of
the smaller multimeters such as this which are described
AVO produced the "70 series" range of analogue pocket meters with 2000 Ohms/Volt sensitivity and 3 inch scale lengths at the beginning of the 1970's. The following is from a 1972/3 trade catalogue.
For further information have a look at my pages on similar AVOmeters here