What is this front brake?

A mate has just got a 'barn find' Triton with this front brake in it. Can anyone help us identify it?

Slightly darkish pics, but it looks like its going to be an early manx conical hub and brake.
Brake plate is likely sls magnesium, and the hub might even be the early thin STEEL one.
Anchored to a peg screwed into the back of the fork slider.

A photo inside the brake plate will confirm.
Even the brake shoes are magnesium.

Brake linings have seen some action, judging by the angle of that brake lever !

I'd take a flying punt at a late 30s Inter!

The anchor point for the brakes for the girder forks is different to the ones for the tele roadholders,
so it depends on how that bit has been done, need to see a detail pic of that.

BTW, these type brakes were optional extras for many models both prewar and postwar.
Durned expensive though, so very few were sold as options (?).
That slim alloy rim makes it look like it could well be a full postwar wheel and brake.
Is it a Dunlop rim ?