Thats a brake lever of a GT750 water bottle JohnnyO
It is what I am using for the Quad-leader on my Maico MD400SS Roadie.
I had a Royal Enfield 750 Super Meteor built middle 'fifties on the road for a while which had a twin front brake setup with a dual cable arrangement as in this pic.
I found it to be an excellent setup, nice & soft pressure, powerful, and never grabby, even when cold.