SN10269 belongs to Scott (who had actually advised me a year ago of his machine ... sorry Scott!)
He says a retired arcade operator had it sitting in the back of a warehouse since the mid-70's. It is still partially working: Screen turns on but some game elements (Rocket, enemy saucers) do not appear. He is starting an after-work hobby project to diagnose and repair the various problems with it.

Click the thumbnail to see a larger version