[Adriano Baumgartner]

Not really my field of interest and expertise, however JJ could be "Junkers Jumo"?

Am sure some real experts here on engines and this kind of "puzzle" will help you here. There are men who really know about that and can track the werknummer of the aircraft and therefore the full history of the crew and last flight only matching those part-numbers of pieces like that.

As Gilles remarked, perhaps interview with the old locals or relatives, or researching the old magazines and files (Police, Hospitals) of the nearby town can be of help...Cemiteries can add further info, if the crew was buried nearby....

Yours
Adriano B.