(Note: Measurements are outside max. dimensions unless stated otherwise).
20th Century : Edwardian period plain thread escutcheon.
OUTSIDE
Height 20mm. (3/4")
Width top 11.5mm. (7/16")
Width base 6mm. (1/4")
Depth 5.5mm. (3/16")
Thickness (variable) 2mm. (1/16")
KEYHOLE
Height 17mm. (5/8")
Width at top 7mm. (1/4")
Width at base 3.5mm. (1/8")
Usually glued in or could be pinned from inside flange.