Early Leinen with lever-operated screwcutting and feeds gearbox
From it's introduction the L4 was continuously developed and improved with several changes to the drive system and stand was well. Although the apron and screwcutting gearbox were different, the headstock, bed and compound slide rest of early versions were remarkably similar to those used on the lathes made during the 1950s and 1960s. The first stands, in heavy cast-iron stand, were well appointed, having both a full-length wooden tool tray and storage for collets and changewheels beneath. Over the years the stand gradually changed, becoming more enclosed until finally replaced by a much more modern-looking full cabinet at some point in the early 1950s.
Instead of a cumbersome, rear-drive countershaft, the flat-belt drive to the headstock came from underneath; the difficulties of engineering the installation within the confines of a traditional stand were overcome by shaping the headstock-end leg to hold a beautifully made (and complex) multi-plate clutch/drive unit.
Although at first just a changewheel model was made, within a few years a full screwcutting gearbox version was introduced (at first with lever change and dials) and became the standard machine - the changewheel lathe retaining a gearbox-like housing at the headstock end of the very large diameter leadscrew. Early types with a screwcutting gearbox have been found labelled as the Model D23LZN and were able to generate a wide range of pitches without needing to alter the setting of the changewheels. Inch threads from 9 to 120 t.p.i, metric from 0,25 to 3,75 and MOD from 0.25 to 3.75  could all be generated. Included with the box was a set of 10 change wheels: 32, 35, 35, 40, 60, 90, 95, 110, 120 and 127t.

One of the earliest versions discovered with the first type of integrated drive system, a lever-change screwcutting gearbox and open headstock

Leinen Model D23LZN. This had a full screwcutting gearbox able to generate a wide range of pitches without needing to alter the setting of the changewheels. Inch threads from 9 to 120 t.p.i, metric from 0,25 to 3,75 and MOD from 0.25 to 3.75  could all be generated. Included with the box was a set of 10 change wheels: 32, 35, 35, 40, 60, 90, 95, 110, 120 and 127t.