A drill of unusual and special design, the Ruka is almost certain to have come out of the RUKA optical works - Runge & Kaulfuss Optische Werke in Rathenow. Germany. Rathenow was long a centre of the German optical industry, its beginnings traced back to March 10th, 1801, when Rathenower Pastor Johann Heinrich August Duncker received the Royal Prussian Privilege to run an optical industry institute - Dunckers and Wageners - while being granted, at the same time, a patent for the multi-purpose machine he had recently invented.
Founded in 1920, ten years later Runge & Kaulfuss were to move into a new factory at Jägerstraße 24 (today Goethestrasse). One special product was their Scheitelbrechwertmesser - a measuring device used in ophthalmology and ocular optics to determine the "apex value" - this then being used to determine the refractive index of optical visual aids such as spectacles. Ruka also manufactured a range of glass drilling, cutting, grinding and polishing machines - their sales being to the general ophthalmic and optical trades. In addition, they also made the expected optical goods - military range finders, microscopes, binoculars and instruments for testing eyesight - one special achievement being the RUKA-VARIATOR, this being used for (if the translation from the German makes sense) "the subjective determination of spherical vision defects, astigmatism and the position of the cylindrical axis. The patented design of the optical system made it possible to place the exit pupil where the lens to be worn later was to be located".
Made in several forms, the Ruka drill presses were usually equipped with a special vice or clamping fixtures and intended to drill glasses or frames - the fixtures able (as in the example below) to be rotated around two axes with graduations on the respective arbors. Before WW2 many glasses were frameless, with the bridge and the earpieces fixed by screws passing through the glass lenses; the holes were made with special 3-edge drills from both sides of the glass to prevent breakage, the  table of the machines used allowing the glass to be turned over and so give a constant gap to the edge. Other larger makers active in Rathenow were Ruge und Kaulfuss,Nitsche und Günther and Weco (Wernicke) - these big three making the whole range of machines need for optical work including ones for drilling, glass edging and grinding, etc. together with some special and very ingenious mechanisms for cutting lenses with a diamond to special oval or oblong shape.
As a specialised product therefor, the Ruka drill presses would only ould have been found in the workshops of  opticians or associated trades, as might the rather similar English-made WA-CO - both mirroring the traditional "swan-neck" design as used from early in the 19th century and made in smaller versions by many companies including, in England,  Denbigh. When was the Ruka it made? There are several conflicting pieces of evidence to consider: unlike the WA-CO from the late 1940s, it would probably have been made during the 1930s - the town of Rathenow being in communist hands after WW2 and the optical industries nationalised. However, there is no reason to think that it could not have been made in the early 1920s, for the gloss black finish has the look of japanning - or an imitation of the process - that although widely used on all manner of goods until the early years of the 20th century, had largely died out by the 1920s. Is the plating on some small parts nickel and not chrome? Certainly, the vice-cum-clamping assembly has that  "soft" look to it - and are signs of a copper coating below the nickel turning to verdigris? If so, that would place the drill before 1930, the earliest year in which chromium plating was widely used.
Weighing 4 kg, the Ruka was of much heavier construction than the very light, small drill presses made for amateur use by such as Champion - though lacking a built-on motor it would have needed to be driven in the same way - by a motor mounted on the bench behind with a belt passing upwards to run over a pair of jockey pulleys that guided it around the spindle. As just a single pulley was fitted, speeds would have needed to be arranged in some other way - a considerable inconvenience for the buyer and a hint that the drill was indeed from an earlier era when such considerations were, well, not so considered. However, in a small, crowded workshop, it may well have shared its drive with other machines, being connected, from time to time, as required…..