A forerunner to the better-known and heavily modified Types 53 and 53N, the Type 51 incorporated many of later machines' features but with a less generous capacity. Built in small numbers during the 1940s (alongside the Type 52 whose production it appears to have overlapped) today the machine is seldom encountered. Based on a patented design, the column, drive system, knee and table were conventional enough (though massively built and to a high specification) but the head was possibly unique. Carried on the end of a sliding horizontal cylinder 240 mm in diameter (that could also be rotated and locked at 15° intervals), the bevel-gear driven head was fitted with an ISO 40 nose (VSM 33931, size 44, or DIN 2079, size 40) and a positive, 2-key drive. In and out head travel was 300 mm and rotation was possible through 360°. In order to accommodate horizontal milling, a pair of 50 mm diameter ram supports pulled out from the face of the head with the cutter arbor (supplied in a number of sizes), being driven from the horizontal spindle nose.
With travels of 500 mm longitudinally, 160 mm across and 400 mm vertically the  750 mm x 215 mm table carried 4 T-slots with a surrounding coolant rough.  Both slow and rapid feeds were fitted on the horizontal travels (the former spanning 17 to 130 mm/min and the latter 170 to 1300 mm/min) with just a slow feed - from 17 to 130 mm/min on the vertical
Driven by a 2-speed 1.3/2.2 h.p. motor running at 1000 and 2000 r.p.m., eighteen spindle speeds were provided that spanned 43 to 2500 r.p.m. 
Standing some 1550 mm high, the Schaublin Type 51 was around 1300 mm deep from the tip of the cross-feed handwheel to the back and weighed 1000 kg.
The Type 51 has also been found marked, on the right-hand face of the column, as a Steinel-Schaublin  - though if the machine was built by Steinel, or just badge engineered, is not known..