Marketed during the 1960s and 1970s by Geo. Kingsbury (Sales Ltd) of The Causeway, Staines in Middlesex (one-time importers of Index Auto lathes) the origin of the "Hydro" Model L lathe is uncertain. However, based on its design and general appearance, it might well have come from Spain - a country that saw a huge expansion of its machine tool industry from the 1950s into the 1970s.
The "Hydro", in the form shown below, was intended for "second operation work", a term that encompasses a variety of tasks but typically part of a production process where items semi-finished on one machine - perhaps a Swiss Auto - could be further machined or modified. As the work would have involved hundreds of identical components, the lathe was equipped with quick-action, lever operation of the top and cross slides and tailstock spindle. Each movement could be restricted by screw stops and so the lathe very easy to set up for operation by an unskilled operator - who merely had to load the job and operate the slides. To further speed things up, the standard machine was equipped with a foot-controlled motor switch and brake that, when operated, also opened the (dead-length) spindle collet for the loading or unloading of a job.
Cast in one rigid piece with the bed, the headstock doubled as housing for a 3-speed motor, the spindle running in a matched pair of high-precision taper roller bearings. Although this arrangement was inexpensive to manufacture and did away with the need for drive belts and a speed-change gearbox, one can only hope that the motor was an easily-replaced unit and not, like those incorporated in many Arboga drilling machines, an integral part of the structure and both difficult and expensive to repair.
On a conventional lathe, to maintain the headstock-to-tailstock alignment as the sliding carriage wears the bed, separate sets of ways for the carriage and tailstock are normally provided; on the "Hydro" just a single pair of ways used but, as slide rest assembly was bolted down and infrequently adjusted, this was a perfectly satisfactory arrangement.
Mounted as standard on a fabricated steel stand with chip tray and an attached coolant unit, the lathe had a centre height of 3.5 inches (89 mm) and a capacity between centres of just 6 inches (152 mm). As such, it might seem that the Hydro was of very limited capacity - but was, in fact, of an ideal size for the work it would be expected to tackle. The spindle carried a 1.75" x 16 threads-per-inch nose, was bored through 0.78 inches (20 mm) and had a maximum through-the-collet capacity of 0.75 inches (19 mm). The three spindle speeds from the direct-drive, 0.25 hp., 0.4 h.p. and 0.5 h.p. motor were 750, 1500 and 3000 r.p.m.
Fitted with front and back toolpost, the "forming" or "cut-off" cross slide had a travel of 0.625" (15.9 mm); the top slide could be swivelled 45° each side of central, had a travel of 2 inches and was fitted with a toolpost capable of holding tools up to 0.5 inches square.
1.25 inches in diameter, the No. 1 Morse taper tailstock spindle had a travel, under the control of a rack-and-pinion lever-operated drive, of 3 inches.
The "Hydro" was offered in three versions that differed only in the details of their specification: the Mk. 1 standard as described above with draw-in dead-length collets; the Mk 2 fitted with pneumatic operation of the collet closer and a more powerful disc brake and supplied with a set of ten Burnerd "Multi-size" collets - adjustable to take inch and metric bar stock from 1/16" to 1-inch in diameter - and complete with a power-operated collet chuck. The final option was the Mk. 3, this being identical to the Mk. 2 save for a toggle-controlled, power-operated 4-inch Pratt 3-jaw chuck arranged for external gripping only.   
Standing 38 inches (965 mm) high and needing a floor space of 25 inches by 48 inches (635 mm by 1219 mm) the "Hydro" lathe weighed approximately 5 cwt ( 252 kg).
While the concept of a second-operation lathes goes back to the original maker of bench precision lathes, the American Stark Company (and most other makers of similar types offered such a conversion) machines contemporary to "Hydro" included the Weiler MFU-260, the Smart & Brown Model L and Accuratool.

A standard Mk.1 "Hydro" lathe with draw-in collet closer
Data on the "Hydro is lacking and it is not know if, like many similar 'precision plain-turning bench lathes' it was offered with the option of being set-up in the usual three different ways: with a screw-feed compound slide rest as a lathe for use by a toolmaker doing essentially simple but very accurate one-off work; as a "second-operation" lathe equipped, as here, with the slide rest and tailstock fitted with lever operation and, finally, as a full-blown production lathe in which case the usual fitting would have been a bed-mounted indexing capstan unit and lever operation of the collet closer. However, depending upon the job in hand, any combination of parts could be used and the so lathe's versatility best exploited.