RE: What is this diesel engine
It's a PAW 1.49 RC BR or TBR from about 15 or 20 years ago.
I think the prop spinner nut is from a later version.
The BR or TBR possibility should be resolved by looking on the LHmounting lug.
Here's mine.
Great engine to use and economical on fuel. The engine shown consumes about 1 cc of fuel per minute during normal in-flight idling.