Images of 3 more general service KC buttons added:
Joseph Steer, Birmingham
Harcourts Ltd, Birmingham
Hobson & Sons, London (small size)
Joseph Steer, Weaman Street, Birmingham had a patent registered in 1853.
A 1926 advertisement was sold on ebay:
The "Twinhinge" a new hinged stair eye with a novel method of fastening. No spring or turnbutton is used.
Full particulars on application to leading factors or to the manufacturer.
Joseph Steer, 43/44 Weaman Street, Birmingham
This link has details on Harcourts:
https://www.gracesguide.co.uk/Harcourts