Yep it does have a NAD sticker and brown contact which I have not lifted if yet.

I've been trying to get this roughly working so I can tell what bits I need to buy.  Thanks to Simon yourdreamin for help with a schematic which will make things considerably easier.

Taking the advise that most EM problems stem from score reel and player units I did some examination and cleaning of switches.  Each score real has four zero position switches! (Two NO and two NC - seems a bit excessive)  One was out of adjustment. I removed about 1/4" of dust and lint over everything. Cleaned the player unit in the head box and checked switches. Some of the switches are very tough to get into to clean. Got to a stage where I could get a game to reset and start - enough to verify most things are working but midway through this test the game went into game over mode.  Enough is working to be happy and to confirm it needs a very thorough clean and examination.