[Milsurplus] Russian set, help needed.

[Military1944 at aol.com]

Ok, any help on this one then. 
 
plate states:
 
Made in USSR
SRP-5
 
Set is a direction finding set, 7 tubes, tuning 186 to 750kHz, AM with bfo  
as well, wide and narrow i.f. setting, large illuminated 0-360 deg scale with  
two moving outer rings and a moving pointer. Metered to measure lt and ht  
voltages. Sockets on the side marked GONIOM and SELSYN, obvious what these  
drive. 
 
Strange thing, though plate states MADE IN USSR (in English) all the  control 
lettering is also in English.
 
So, anyone any idea of date, service, circuit etc etc. 
 
Pic at:  "www (dot) qsl.net/g4bxd/russian.htm"
 
cheers, Ben G4BXD