Had to look twice when I first see this, but after looking into the company it is not as sinister as it first seems, I‘m glad to say.
The hinges were designed to keep open doors open and then once moved past the "detent" will close the door, the name "Slave" was because it did the work (holding open/self-closing) for you. Today probably more thought would have gone into that name.
The fact is James Adam & Sons where donating to the local Church’s, suggesting they are less likely to be wildly pro-slavery.

- Blackfriars Road, James Adam & Sons.

- Blackfriars Road, c1913. James Adam & Sons.