Turned wooden cylinder

Circular turned piece of wood from end grain wood. with a centrally bored hole, and the main body tapers to one end. There is turned groove around the middle as the possible seating for a gasket, seal or washer. Written in it in pencil "LOWER BOX", "P", and possibly "5 1/2 " MAX 21" WHEN [illegible]". This may be the valve for am elm tree pump used for removing water from the bilges in the lower hold of a ship.