Thanks folks. All suggestions welcome.
John, no it isn't tapered.
I called it a stopper because...
a) that's what it looks most like
b) a couple of hoary old bottle-diggers said it was
I was a little concerned by the fancy little ridge design thingies around the cylinder. I thought that they might cause it to stick. So the idea that it isn't a stopper is fine by me.
But I can't really see
a) how such a door/drawer knob might be attached
b) why it would be in a rubbish tip if it isn't broken - unless, as you say, Fox, there's some metalware missing and that's what got broken. Although I would have thought that - back in the 1930s - someone would have mended it rather than chuck it away.