I am not quite sure of the use of this as the central hole in the top has an internal tube aligned with the one in the base. Possibly to take some metal fitment. There is a similar base though with jut one hole in the catalogue of the Beeson collection in Birmingham Museum Alabama #364
Dimensions: H 5 ⅜” W 4 ⅞” square
Condition: Chip to one top corner and chip to another restored