So that would be Robert Dundas.....

Could have been the 5th as well - also a Robert Dundas (1835-1904).

Have 3 covers addressed to the Right Hon Viscount Melville - all from the Year 1881 and addressed to his Office at 7 Portugal Street, Grosvenor Square, London.

My question is - Which Viscount is this - there have been 10 to date ?

Pics added.....