Uhh, I was, of course, referring to the 912 in the photo, not a 910.
The 612 is a bit like your 10-12 and the 912 in general layout but it has 3
rotary controls to select test voltage/current, filament voltage and meter
shunt and then a bank of 10 lever switches [one for each tube pin] that
connect the pin to common or 'test' or open or filament supply. The levers
are flicked from common [the rest postion] to test one at a time to check
for shorts and then all active elements except cathode are set to test and
the 'test' button pressed for measuring emission.
On the 912 it is not obvious how the tube terminals are connected to the
appropriate test circuits in the tester.
Your 10-12 is pretty obvious how it is done with the added convenience of
push buttong shorts test.

Neil

"Phil Nelson" wrote in message
...
I am curious about this precision 910 tester. I have a 612 which is not
unlike this, but it has 10 lever switches to select the connections of the
10 tube terminals.

Similar to my 10-12?

Phil Nelson