Internal and Traverse Grinding Attachment.
The quickest way to wear out any lathe is to use it for unprotected grinding - perhaps that's why so many makers were keen to encourage its use for this damaging activity  - and Potter offered the usual range of slide-rest mounted units to convert their lathes into useful little grinding machines.
The unit shown above was intended for light, internal grinding and featured completely enclosed, dust-cap protected bearings which were separate from the hand-held sliding shaft that moved the grinding wheel to and fro.

Universal Grinding Attachment.
This accessory (which accepted wheels up to 3" in diameter) was fitted to a base which could be moved up and down through a rocker mechanism which was claimed by Potter to be a design unique to them. The spindle was fitted with dust-sealed double-row ball bearings capable of letting the (unguarded) wheel attain speeds as high as 25,000 rpm.