THANKS ED.
Try this site http://www.agtannenbaum.com/index.html They have your tester listed, if I had a copy I would send it to you.
ED:
Tried to contact you dirctly, but message was returned with "unknown" address. I have copy of Operating Manual for this unit. Email me for information. BTW -
your unidentified tube is a 6C5, according to the scematic. Bob