This nicely-executed 5 cc diesel was submitted by my valued Spanish friend Jesus Ortega Delgado. He voiced a suspicion that it might have been made by students attending the ELIZALDE Aircraft Company aviation engine school. He suggested a date of 1945, but to me the engine looks far later than that - I'd place in in the mid to late 1950's myself.  Any better suggestions?  If so, please use the webmail address which I’ve established for this specific purpose.