Based in Luton, little is known about the background of the Clark's Engineering and Machine Tool Company save that, starting in the late Victorian period, they manufactured a range of conventionally designed lathes, milling and drilling machines. Of the lathes, plain-turning, screwcutting and capstan-production types were offered - though few of any type seem to have survived,  the only example known to the writer being in the Pewsey Railway Heritage Centre. As machines by Clark's Engineering are little known - and literature about them scarce - if you have one I would be delighted to hear from you.
The Clark's lathe below appears to be of around 6-inch centre height and perhaps 40 inches between centres - and of design as commonly found from around 1870 onwards.
Happily, while many makers at the time - dozens of them - failed to put any identifying marks on their products (possibly because they were factored or resold through larger agents who insisted on attaching their own badges) the Clark carried its own distinctive maker's badge. Pointers to its age include crank handles fitted to the cross and top slide feed screws that both lacked micrometer dials - or any form of protection from swarf and dirt  - and the spindle end thrust taken by a plate mounted on posts outboard of the left-hand bearings. However, instead of being very coarse as was common at the time, the pitch of both the leadscrew and backgears is relatively fine, pointing to a lathe probably made later than 1890. An interesting comparison can be made with the lathe-and-morse-co machine of two decades earlier that incorporated several interesting and novel ideas further developed in lathes of the Clark type.
While screwcutting was by conventional changewheels and a tumble-reverse mechanism, power cross feed was of yet another contemporary design, being arranged by a rear shaft, driven from an extension to the rear of the screwcutting changewheels. Power was transmitted from this shaft to the cross-feed screw by the usual worm-and-wheel gearing. Engagement was by a small, two-handled lever on the face of the apron that tightened a cone clutch at the rear of the cross-feed screw. A single lever, positioned in line with the front headstock bearing, had a series of spring-and-ball-located positions, presumably to engage either screwcutting or the rear-mounted power-cross-feed drive shaft.  Although largely abandoned by the end of the 19th century, a few machines did continue with this rear-drive arrangement into the 1950s including three models for amateur use: the 1935 English Pools Major lathe, the 1940s Mellor and - probably its last appearance - the early 1950s Portass "Window" lathe.
And still they turn up. In 2022 another Clark's Engineering lathe was discovered - complete with a wall/ceiling countershaft system -  in what may well have been its first home in the early 1900s, or even earlier. Pictures can be seen low down on the page..