Made by the Riken Machine Tool Company of Japan the 70 mm centre height by 267 mm between centres Riken was absolutely typical of late 19th until mid 20th century precision plain-turning lathe design* as originated in America by Stark. However, whilst most machines of this type used a bevelled-edge, flat-topped bed to locate the headstock, compound slide, tailstock and other bed-mounted accessories the early Riken differed in employing a single central T-slot with one 90-degree and one angled side. Whilst no doubt adequate for the light cutting forces involved this would have sacrificed a considerable amount of rigidity in comparison with the conventional arrangement that clamped over the bed's full width and the angled sides. In respect of the bed casting and appearance of the slide rest the lathe was very similar to the appearance of the 1930s Schaublin range - indeed, it is easy to confuse the two. The Riken was built in at least two versions with a later model using the much simpler and more effective "full-width" bed clamping system employed on the Schaublin.
Collets were of a nominal 12 mm diameter (11.8 mm actual) and pulled into the headstock spindle by a draw bar.  At 80, 64 and 48 mm across their crowns the 3-step of the headstock pulley had diameters identical to those used on the Schaublin 70 countershaft. As usual, the largest diameter headstock pulley was to the left and with its outer face drilled with indexing positions - in this case two rings of 36 and 60 holes. The indexing pin was well supported - it passed through the end face of the headstock casting - and could be further stabilised by being locked with a convenient thumb screw.
Fitted with knurled-edge micrometer dials the slide rest (stamped with the Riken name) used covered ways with the cross slide being a full-length type (that helped to even out wear and impart extra rigidity) with a very reasonable 69 mm of travel. On this type of lathe the maximum length of cut is governed entirely by the travel of the top slide and in this respect the Riken fell down, the amount of movement available, just 48 mm,  being somewhat less than useful. In addition, lathes of this type were invariable conceived as multi-purpose machines able to be employed in both precision toolroom and production use. As a consequence they often had arrangements on the headstock to take a lever-action collet closer and T-slots machined down the front or back of the bed (and sometimes both) in order to carry various accessories including thread-chasing and power-feed attachments. The fact that the Riken's was not so equipped suggests that the designer's brief was to produce a simple but accurate lathe for use in repair shops and for one-off jobs.
If any reader has a Riken lathe the writer would be interested to hear from them.
*Derbyshire, Levin, Stark, American Watch Tool Company, B.C. Ames, Ballou (sometimes found badged as "Waterhouse Electric & Mfg. Co.), Ballou & Whitcombe, Wade, Pratt & Whitney, Rivett, Cataract, Hardinge, Elgin, Hjorth, Potter, Remington, Sloan & Chace, Waltham Machine Works, Van Norman, Bottum, Engineering Appliances, Pearce, Sawyer Watch Tool Co., UND, Fenn-Sadler. and the "Cosa Corporation of New York"
Riken Continued here