Walther lathes were manufactured by  "Walther Werke" a company based in Oberrad, a town close to the city of Frankfurt, Germany. During 1943 the factory was destroyed by bombing and, shortly after the war, Walther were declared bankrupt. Today, rebuilt, the former plant houses a museum about the history of Oberrad: http://www.heimatverein-oberrad.de/
Shown below is a typical product of the company, a short-bed, very heavily built lathe of the "production type" - that is, without a leadscrew for screwcutting but fitted instead with a feed shaft to drive the carriage. In order to enhance the lathe's intended function it incorporated an unusual feature, the use of two P.I.V. Antrieb Werner Reimers mechanical variable-speed drives - one for the main spindle drive and another (much smaller) to power the carriage-drive shaft. Hence, it was possible to not only vary the spindle speed by turning a car-steering-wheel-like-control on the face of the headstock but also, simultaneously and at a different rate, change the rate of carriage travel by turning a smaller wheel of the face of the feed gearbox. Like the similar (but differently-driven) mechanism on the Hardinge HLV and HLV-H toolroom lathes, this arrangement allowed a job to be machined at the optimum rate for its diameter, material and surface finish required by the simple, time-saving manipulation of just two controls.
Founded in 1928 by Werner Reimers, P.I.V. Antrieb Werner Reimers GmbH, has over 500 patents and remains of the largest industrial drive manufacturers in the world, though now owned since 2002 by the Brevini group  when its name was changed its to P.I.V. Drives GmbH. The P.I.V. is not a complicated device and identical in function to a number of other expanding-and-contracting pulley types; however, instead of a belt, a wide type of "chain" is used, the whole assembly running in an oil bath and designed for continuous, heavy-duty use.
The owner writes:
I bought my Walther from an Ebay auction and, when I first saw it, realised that it was in very poor condition: most of the paint was missing, oil was leaking from the two gearbox, the belt transmission from motor to spindle was deranged and the automatic feeds didn't work - this was a machine that had been run into the ground by the previous owner who had used it only to re-machine car brake drums.
Once removed to my workshop I realised that the use of two PIV drives was something rather special and I thought that perhaps the makers might have had some relationionship to the old-established German gunsmiths of the same name. As so little information was available it dawned on me that this could be an example of a "last Mohican" - and decided (despite its terrible state) to refurbish it.
One interesting problem that turned up during the rebuild was a missing lock nut on the friction coupling used to drive the carriage; this used a M32 x 1.5 mm pitch left-hand thread - a size impossible to find today and one that needed to be specially (and expensively) machined. For the paint I decided on a very tough, long-lasting 2-component Epoxy.
A fuller account of the rebuild and the some of problems encountered, in German, can be found here.