Here’s an intriguing Wotizit sent in by reader Dave Causer of England. Dave acquired it some years ago from Mike Clanford.  Mike thought that it may have been of Czech origin, but wasn't sure. Dave confirmed that all the threads are metric, which is consistent wih Mike’s views.

The measured displacement of the engine is 3.2 cc, based on a very long stroke. The complexity of the main cylinder casting would seem to indicate something more than just a "one off", but it could nonetheless be a home-build by a model engineer having better-than-average foundry skills. Most of the construction is good, but the piston/liner fit as received was poor, implying a builder who had not yet fully acquired the technique for lapping piston/cylinder fits to diesel standards. There were also a few issues with the structural integrity of the assembly.

The engine required a fair bit of intervention by Dave to make it into a dependable runner, further suggesting a home-build by someone who was feeling his way. Once sorted, it proved to be even easier to start than a Mills and ran beautifully with great flexibility. However, there wasn’t much power on tap.

Some years after this wotizit was posted, reader David Hill got in touch to say that he had an almost identical engine which was clearly from the same maker, although it had a different carburettor and prop driver.  Measured bore and stroke of David's example are 14 mm and 21 mm respectively for a displacement of 3.25 cc. The main takeaway here is that the engine is not merely a "one-off" - a few examples seem to have been made, suggesting at least an intention to put the engine into production. 

If anyone has any suggestions regarding the origin of this unit, please get in touch!