Model No. 641.
Only identified by the work FUSED on the lid, the manufacturer of this item remains a mystery.
Plug pins are unsleeved, so this plug is at least 30 years old, sleeved pins being instroduced in 1984.
Both the flex frip and fuse are missing. Pins are marked L N and E. The only other mark is the number 28, upside down just above the flex grip area in the base.
The lid is secured with a single screw, black in colour.
NT probably for Non Track.