Vintage GERTSCH Deviation Monitor Ham Radio Vintage Electronics

Description

here we have a
Vintage GERTSCH Deviation Monitor Ham Radio Vintage Electronics
My only testing done is to power it on, and after some fiddling , as I am unsure how to operate one, I got a green dot.
This is all the testing I have done.
As I have no idea how to operate or test it, other than powering it up, I am selling it as is with no returns
Thank you for looking
Please see pictures for cosmetic condition