This is an example of the marks and work of John Mair of Calcutta. As can be seen from the below report, he returned to Great Britain in the late 1790's, apparently having made his fortune.


The Scots Magazine and Edinburgh Literary Miscellany of 1815 has this report of his death.
12th January. At London, in the 56th year of his age, John Mair, Esq. a native of the parish of Rhynie, Aberdeenshire, justly and sincerely regretted, by an affectionate family and numerous friends, who ever held him in great estimation. Mr Mair went to Calcutta early in life, where he followed the profession of a jeweller with success, and the greatest respectability ; and returned to Britain about eighteen years ago ; since which time, his whole life has been occupied in doing disinterested acts of kindness to his friends, and providing for many of his young countrymen. Justly may it be said of Mr Mair, that few men, with his means, ever did more good ; for his heart and purse, with great modesty, were ever open to distress.
Trev.