Hydraulic copying attachments were widely used until the 1970s as a cheap and efficient way of mass-producing, with unskilled labour, small batches of components with simple profiles. Harrison offered a conversion kit for most of their lathes but preferred customers to buy the unit ready installed on lathes of 11-inch swing and above. The device did not interfere with ordinary turning - and a lathe so equipped was every bit as versatile as one without the accessory.
Some lathes had the tank and pump unit fastened to the back of the lathe and some to the tailstock end but much more common was for the unit to be supplied as a separate item, allowing the operator greater choice  as to its positioning..

The 13-inch lathe was much more heavily built, carried its motor inside the cabinet and had a distinctive, flat-topped headstock and a combined clutch/brake control protruding near the lathe bed at the bottom right-hand corner of the screwcutting gearbox. In this application, instead of being fastened to the stand, the Hydraulic pump and tank are shown as separate units.       

An 11-inch swing Harrison fitted with a separate Hydraulic Pump and Tank at the tailstock end of the bed - the long rectangular tank fastened to the back of the lathe was for coolant.  The 11-Inch lathes had their motors mounted externally; the 12-inch and 13-inch versions carried theirs inside the stand on a hinged plate.

An 11" inch swing L5A Hydraulic Copying lathe fitted with its distinctive "chuck" guard. The layout of the switches on the electrical control panel indicates that this particular machine was fitted with a two-speed motor.

Travelling Steady.
Like other Harrison lathes the top slide could be rotated 360 degrees on the cross slide, which was of the "short" type, with protective tin covers over the front and rear potions of the cross-feed screw; however, instead of the expected superior-type of tapered gip strip on the cross slide, an ordinary flat inset was used, adjusted by pusher screws.