SSIP lathes are very rare, and few can have been made. This is the SIP No. 2 lathe 80 mm centre height and 200 mm between centres. Not an ordinary high-precision lathe, but one specially constructed for the automatic correction, checking and measuring very high quality screws, thread gauges and taps, etc. It was fitted with an automatic leadscrew corrector and equipment that allowed it to compensate for errors developed, for example, during hardening of the parts being tested..  Like that on an ordinary G.Boley precision lathe, the leadscrew ran down the centre line of the bed and was completely protected from the wearing effects of swarf and dirt.
The lathes carried a plate stating that the optimum temperature they should be used at was a rather cool 62°F (16.7°C) This SIP lathe, and the one shown below, make an interesting comparison with that made by Bryant Symons in England. If you have a SIP lathe, the writer would be very interested  indeed to hear from you.

SIP No. TF4 special lathe with a 135 mm centre height and 400 mm between centres. A larger version, with a 155 mm centre height, was also listed. Like the Bryant Symons lathe, this SIP lathe had separate front and rear bed sections, the front carrying the carriage and the rear the tailstock. It may also have been fitted with an automatic forward/reverse mechanism to the carriage drive.
The spindle nose on this lathe is rather special. It starts with about half-inch long 32 x 2 mm thread with, immediately behind it, an external taper starting at about 35 mm in diamter and ending, 40 mm later, with a diameter of 47.5 mm. There is also a square shoulder of 80 mm diameter with opposing 'keyway locking cutaways' about 30 mm wide. The lathe has survived with an older 140 mm diameter 3-jaw chuck mounted on a backplate adapter that matches the spindle nose design, and two 240 mm diameter faceplates that mount directly on and match the spindle nose.

The TF4 had separate front and rear bed sections, the front carrying the carriage and the rear the tailstock. It may also have been fitted with an automatic forward/reverse mechanism to the carriage drive.

SIP high-precision "Universal Circular Dividing Machine" - fitted, as were all such circular and linear machines, with corrected leadscrews and worm-wheels.