Anyone ever run across this? I couldn’t find anything on it

https://w2hx.com/x/TTY/43A-1%20Test%20Meter/20221202_141257.jpg

I picked it up thinking it could make a nice meter for tty loops. But I wonder what its original purpose was. I would have thought something TTY related would be +/- 100mA not just 0-100mA

73 Eugene W2HX
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