[Amps] A little petition, but Off topic

[GGLL]

    Sorry for this message being off topic, but considering the 
experience of the rest of the people in this list I give it a try: maybe 
somebody can help me with an old piece of test equipment I have; I own 
(gift from my radio teacher years ago) an old VTVM, in very good shape 
and working, it's a Radio City Products model 657A.  The meter is  6.5" 
by 4.25", very easy to read. Measures ACV, DCV both upto 1500V, 
resistance and capacity.  Double triode (12A?7, don't remember if T, U, 
or X)  and double diode (6AL5) inside.
Instrument faceplate says: Radio City Products. Co. Inc., Easton, PA, USA.
   What I want to get is an operating manual with the schematic for it, 
can you help me with this, or a place where I could get it, either a 
manuals library, another list,  or the Internet?

Thank you in advance
Best regards
Guillermo - LU8EYW.