William Permain was an art dealer who originally came from Liverpool. He was in business as a dealer in Pall Mall Court from the 1860s, and went into partnership with the print dealer T McLean in King Street; he was a member of the Printsellers Association. He specialised in early English watercolours and in the Norwich School. He died aged 69 on 5 May 1910.
Times, London, Friday 6 May 1910, p. 11.
Source of this information: http://www.whistler.arts.gla.ac.uk/correspondence/people/biog/?bid=Perm_W&initial=P