The panels were made by Troughton & Young Ltd electrical engineers. There is a calibration sticker in pic 1 dated 17th sep 89 which is I'm guessing just after manufacture of the circuit board which is a much later addition to the panel and seems to tie in with the date that Sheppertons diesels were decommisioned (power house).
Look at the socket tapped from 2 busbars in pic 8.
Despite all my efforts to save the panels, for displaying at the vintage shows I go to with my vintage generators and engines, they were removed and sent for disposal due to the building containing asbestos. This was only part of what was in studio H so you can only guess what was lost in all the other studios, I did manage to save 2 huge 2500 amp ammeters that measured the volt drop over a length of the busbars you see in pics 2, 3 and 4.