Some of the original locks in the house are long gone, but some notable ones have survived. But my, the world was enamoured of paint in the 1900s! Most of the original locks on the house have been painted shut, as have many of the brass window fittings and locks. Even the elegant and cleverly designed window clips that hold the sash windows open have been painted over.
One of the notable locks on the house is the front door lock. It was heavily painted and was quite stiff. I pulled the lock off the heavy front door and had a go at cleaning it up & restoring it. Here you can see the results: before and after. One the back is embossed "Sargent and Co" - and when I googled the name it appears the company is still going strong. I have written to them in the hope they can tell me when the lock was made, which would help us date the house (1880s? earlier?), but alas no response yet. I'll add a comment to this post if I do get a reply!