This image of an unidentified twin ball-race diesel was sent in by a blog site participant who goes by the enigmatic name of “Supercuber”!  He tells us that it is supposedly of Yugoslavian origin dating from the early 1950’s. No displacement is given, but it must be in the 2.5 cc – 3.5 cc range. He has apparently confirmed that it is not a member of the AERO range, but suspects that it could possibly be an OSKAR product. Of course, the possibility also exists that it's not from Yugoslavia at all but from some other country. Note that the prop which is fitted is a pusher item, possibly indicating reverse rotation.

Can anyone out there put a name to this one?