Hayward Brothers, 187 & 189 Union Street, Borough.
Hayward’s coal holes are widely found in London and the provinces. Apart from the patent self-locking plates, they are one of the few manufacturers to insert glass panels to provide light in cellars.
Their large glazed gratings can be found in front of many Victorian buildings.
No idea where I found this one, but a simple walk around and you can find one as well.