TBH I really don't know, that was over 50 years ago and things have moved on quite a bit since then, but when I google Sangamo Weston who were the main manufacturers it shows me very similar looking devices, as do Horstmann gear co. There must still be plenty of them fitted, I once repaired a Horstmann for a gas heating system in a shop. That was fitted with a clock mechanism with jewelled bearings and dated from the 1930's. I especially remember it because it was returned three times and then an engineer came round to demonstrate it wasn't working, it was, it had a gravity switch and they had been fitting it upside down, red faces and apologies.