Powell, Thomas Baden (1786 -1868)
Fairbairn’s Crests (1905 ed.) identifies the stamp as Powell, of Newick, Sussex. The most likely candidate is Thomas Baden Powell, M.A. (1786-1868). After graduating from Oriel College Oxford in 1808, he became rector of Newick parish in Sussex. In 1824 he inherited the Newick estate from his father, James Powell (1737-1824), who had purchased the property from Lady Vernon's estate in September 1812. It remained in the family's possession until 1897. In 1811 Thomas married Sarah Louisa Cotton (d. 1835), daughter of Nathaniel Cotton, and had one son William (1817-1885).
Cf. e-mail from Wynyard Wilkinson, Oct. 2016