I'm revising my guess....it's a Cooper Bessemer forerunner of the LSV-20- and KSV-20- diesels that power the emergency conventional generators used as power back ups in nuclear power plants, to keep the pumps running in case the grid goes down or other bad things happen. There are only so many 20 cylinder engines out there, and it isn't a 645. Well, if it is, then I need a new prescription for bifocals.