All I know right now is that it’s made in 1973. Another instrument I have is from a b727 and is dated 1982. This one I have no clue. Serial number- H 2590. The brand is Amphenol. That’s all the info I can find. I have some pictures.
It looks like the pack temperature gauge for the air conditioning system on the 727
To monitor the operation of the air cycle machines, each has a temperature transmitter at the outlet off its compressor. The temperature sensed is displayed on a pack temperature gauge for each pack. As more air is directed through cycle machine to provide more cooling, more compression is required from the compressor. This results in a higher compressor outlet temperature. Therefore, the pack temperature gauge monitors air cycle machine work load. To protect the compressor from excessively high temperature an over temperature sensor at the outlet of the compressor will cause the pack to shut down if the temperature reaches the limiting value. Another temperature limiting sensor located at the inlet to the turbine.
Here it is on the flight engineer's panel (airliners.net).