Unidentified Stamp

Unidentified Stamp
Dimensions (height x width): 30mm x 17mm
Monogram: C B
Coronet: Earl
The most likely candidate of this stamp is Caroline, Countess Bessborough. In 1849 John Ponsonby, 5th Earl of Bessborough (1809-1890) married as his second wife Lady Caroline Amelia, (1819-1890), eldest daughter of Charles Gordon-Lennox, 5th Duke of Richmond.