Keithley 179A Bench Multimeter - Calibrated
https://www.youtube.com/watch?v=PmslldgJCGsThe price I paid for that meter, and it's sick companion, was under $10, though shipping for the meter was over $20 per unit.
Datecodes are going to be poor on the main chips, as they will have been made batch by batch. Will only be able to tell you which lot of the instruments they were used in.
As an aside I did use some of those meters in the 1990's, and then they were new, and were around $800 in South Africa.
I even have a small amount of those true RMS converter chips around, still unused, and unfortunately only in the cerdip package, so if I need one I will just have to dead bug the pins needed to the TO100 mounting pattern.
