Ended up buying it for $30. Battery charger works.
It appears to be working, I can see RPM, volts and I think timing on one setting.
It will probably work a lot better if I can find a manual.
Needs some more cleaning from sitting.
Contacted Stewart Warner about a manual because you never know, got a very quick response, he said they haven’t made it for decades and don’t have any data on it.
Dane
1986 F250HD SC XLT Lariat 4x4 460 C6-Sold
1992 Bronco XLT 4x4 351W E4OD
1998 GMC Sierra SLE K1500 350 4L60E
Arizona