At the Model Engineering Exhibition of 1946 Coronet displayed three new small precision lathes: the conventional "Diamond" and round-bar bed "Jewel" and "Ruby". Described by the makers as The Watch and Clockmakers Lathe and Multi Propose Machine, the tiny, 1.5" centre height Ruby used a solid steel bar as its bed and a headstock casting that doubled as a mounting foot. A bolt-on motor was optional but, as it carried just a 2-step pulley, the speed range was severely limited. The headstock pulley was overhung, an unusual and rather brave design decision for a precision lathe where the tradition of super-accurate bearings, of hardened steel, honed and lapped to perfection, with the pulley carried between them, had been established for over 80 years. By coincidence, the same decision had been reached by the English Pultra Company on their new range of 17/50 and 17/70 models, also announced in 1946/7. To allow the Ruby to function either as a lathe or a precision drilling and milling machine, it was mounted on a heavy cast-iron base plate formed with a post socket at one end.  With the lathe set as a drill, rather than a lathe, the bed was up-ended, dropped into the socket and held in place by a long through-bolt. The tailstock, already provided with a lever action feed (by the simple expedient of peg passing through a slot cut through the top of the casting) was fitted with a collet-retained faceplate that acted as a drilling table - whilst the (optional-extra) compound-slide rest could be pressed into service as a co-ordinate table for vertical milling. In order to provide the greatest versatility, the headstock was available with a choice of two cartridge spindles: one for ordinary work with an adjustable tapered bronze bush at the front and a single ball race at the back (an arrangement also used, in a non-cartridge form, on most of the Company's wood lathes) and the other, a high-speed unit, with ball races at both ends. The assembly (not unlike that used on the first Emco Unimat lathes from 1953 and resembling a bicycle hub) was clamped into the headstock by a single lever closing down a slot in the casting; hence it could be removed very easily and swapped over. With a 0.314" bore and a  5/8" x 26 t.p.i. nose thread the spindle was designed, like the tailstock, to accept draw-in 8 mm collets.
Beautifully painted in black ripple enamel (crackle-black, a popular finish at the time and used to denote a quality product ) and with all the locking rings and adjusters beautifully knurled, the basic Ruby retailed for £18 : 18s : 6d without a motor (for comparison a backgeared and screwcutting ML7 was first listed at £36). Complete and ready to run the price rose to £24 : 18s : 0d. A compound slide was an extra £9 : 18s : 6d, a 2.5" precision 3-jaw chuck £6 : 15 : 0d, wire collets 7s : 6d each and stepped collets 12s : 0d. Supplied as standard with each machine was the cast-iron base plate, hand T-rest, faceplate, driving pin, collet draw-in tubes for headstock and tailstock and one pair of precision centres mounted on collets. An interesting comparison can be made between the Ruby and the German Saacke miniature universal machine of the early 1950s - through the latter would, no doubt, have cost several times as much.
Using many components of the Ruby, including the complete headstock and tailstock units and a bar-bed, the "Jewel" was arranged conventionally with small splayed feet and a carriage driven by an overhung leadscrew running down the front of the bed. A single swivelling tool slide was fitted with the whole machine looking remarkably like the larger but much cheaper and less desirable Velox from the early years of the 20th century. Both Ruby and Jewel must have been made in very limited numbers, for today they are very rare - even the contemporary Boxford Boxford miniature precision, at an expensive £175, being relatively common today by comparison.
Of more conventional appearance, with a flat-topped, cantilever-form bed, the 2.25" x 6" "Diamond" had a headstock assembly that could be unbolted from the bed and a base that allowed it to be swivelled 10° in either direction from central. The spindle (plain-bearing and ball-race) was, apart from a 11/16" x 20 t.p.i. nose thread, identical to that used on the other lathes and could be exchanged for the high-speed version. A hand-operated feed was provided for the carriage, the leadscrew passing down the centre line of the bed (where it was completely protected from swarf and dirt) and connecting to the saddle immediately beneath the toolpost. Unfortunately, only a single swivel slide was provided (though with an unusually large-diameter micrometer dial) carried on a post that fitted into a hole formed in the front of the saddle. Whilst this provided a quick and easy way of adjusting the tool height (just like the fitting on a Round Bed Drummond) it did nothing for rigidity, the cutting tool being cantilevered well away from its connection with the bed.
Of the ordinary screw-feed type, the tailstock could be set over for the turning of slight tapers and was fitted with a proper compression-type barrel lock. 
If any reader has a Coronet miniature precision lathe the writer would be interested to hear from you.