Looking for a keyhole

I found this old key in the garden 30 odd years ago. It doesn't fit any doors, and now hangs in our outside privy (now a garden shed). The colours on the brickwork show what previous owners of the house thought would be suitable in a privy. The walls could be rubbed down and repainted, but I like it like this. :-)

PiP 1 shows a rusty hinge on our greenhouse door.

PiP 2 shows some rust on garden furniture