They were made orig by 'Bulldog', then later I believe ITE bought the brand/design. I used to have a bunch of then in the shop, single, double and three pole.
IMHO, they were a pain in the butt. Bolt-in, tight panel space, and I wonder if they ever had a SWD rating.
It was 'push-on; push-off' with an indicator in the 'push' part.