I may as well start right out by stating that the identification of this very well-made and refreshingly "different" diesel as a Ten-Sixty-Six product is not secure. The tentative identification is based on a number of structural features which combine to strongly suggest that this is a hitherto-unreported late 1940's prototype from Ten-Sixty-Six Products of Worcester in England. There's no record of that company experimenting with diesels, but that does not preclude the possibility that they did so.
The engine in question is a 2.75 cc diesel which features the highly unusual arrangement of a dual induction system. The main induction and fuel supply are through a conventional sideport intake at the rear, but there's also an auxilliary air-only FRV system controlled by the crankshaft. Even more intriguingly, the FRV intake is adjustable from completely closed to fully open using a set screw.
A full description and test of this intriguing unit will appear in due course on this website. In the meantime, anyone able to shed further light upon the engine's origins is cordially invited to get in touch!