Backplate - Raised Square

(Note: Measurements are outside max. dimensions unless stated otherwise).

20th Century : Raised hollow square platform backplate with 'pastry cut' scalloped edge.

FLANGE:
29mm. x 29mm. (1 1/8" x 1 1/8")

RAISED PLATFORM
20mm x 20mm. (3/4" x 3/4")
Diam. hole 7mm. (1/4")
Total height 7mm. (1/4")

Possibly originated from base to a lamp column.