Bingo, found this on the electrical interweb. It described the two different forms of the caliper: Girling 19P and PB.

And yes, they were also used on Mk1 Lotus Cortinas.

https://www.mevspares.co.uk/FRONT-B...-Cortina-Mk1-Lotus-and-GT-Sep-65-66.html

But no, I'm afraid it doesn't actually help you solve your retainer issue. Even if it does explain the apparent difference I remarked on..

Cheers, Colin

Last edited by hillclimber; 24/01/24 10:40 AM. Reason: typo