My notes show Liverpool 50p is same chip but large key mold.
Chips possibly distributed by John Huxley. Same mold was used extensively in London from 1965 to 1980 approx - notably Playboy and London Victoria.

Howdy Herz has the records on these and the notched samples. My info is from long time casino employees also.

Ladbroke Sporting Club
262 Tottenham Court Road
London

Closed about 8 years ago and then re-opened by Gala.

Jason Skinner's site has scans of most UK chips, including his own chips, mine and Howdy's. Here is the relevant page:
http://www.geocities.com/jdskinner123/lschiplist.html