MYSTERY RACER

A curious racing motorcycle appeared in my mailbox today, of an engine configuration I've never seen.  I have an idea that the chassis is a Smith frame from Australia, which was a scaled-down Norton Featherbed built to house mainly Velocette engines for 250cc racing, and which was based on the Beasley frame from England.  That this machine uses Velocette forks, gearbox, and wheels supports the theory.  Typically, Velo MOV pushrod engines were used in such frames, often with special cylinder heads in bronze or aluminum cast by enterprising tuners such as Carey.  Some frames housed sleeved-down KTT engines, which were certainly heavy but fast and durable.
Australian racers did battle far away from the epicenter of the motorcycle industry; spares took months to arrive, and tuning advice dispensed in a mere trickle from the factories.  So, the 'bush tuners' made their own racing heads, frames, or whole engines.  It appears this curious motor is entirely home-made, and appears to be an 'OP' (opposed piston) engine, in which two oppposed crankshafts move two pistons towards each other in a common cylinder barrel, forming between them the combustion chamber at the top of their stroke.  Fairly common in marine applications and sometimes aircraft, such an engine is very rare on a motorcycle!
There are as many variants on the internal combustion engine through its nearly two-century existence, as there are dinosaurs with outlandish teeth, armor, and body shape.  And, most are equally extinct, for the moment.
Can any readers shed light on this machine's history?