Take some more pics. I need to see the shape of the spindle in that hole. It looks rather like the Ingersoll flattened round, which has an oval tube key. More common ones are hexagonal or half-moon shape.
Look for any printed or embossed markings, and photograph from all angles.
Edit
Now I look enlarged, it is more like a warded cylinder. I don't recognise it.
Try here. There are a few specialist in this line. Send them some better photos if you can't see a match.
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