Unidentified Stamp

Unidentified Stamp
Dimensions (height x width): 20mm x 12mm
Monogram: E M or E M D
Coronet: Viscount
The owner of this stamp was a Viscount or Viscountess, or the elder son of a peer whose courtesy title was that of Viscount. Ethel Mildred Devereux, Viscountess Hereford who died 2 June 1945 is a possibility, though the stamp seems to be much older.