.. someone suggested it was a sex toy .. ouch !
https://imgur.com/a/67YlT
John T.



Pinterest has a similar pic of the sprocket, states it's related to a dairy farm tool. https://www.pinterest.com/pin/496592296384607638
I had Googled "antique farm sprocket tool".
Another Pinterest image, states it's a cistern pump sprocket, pulley.
https://www.pinterest.com/pin/426153183473852990/
Another cistern sprocket: https://picclick.com/Antique-Vintage...060942778.html
Sonny
How about this: https://www.lehmans.com/product/repl...em-water-pump/
Sonny


Hurray !
I think you got it - chain pump - Thanks !
I've never heard of one, though ..

https://www.lehmans.com/product/cinc...em-chain-pump/

John T.