1918 Cover to Duke of Argyll, England.

1919 2+1c War Tax tied by FPO militia Camp Borden, Ontario (SP 13) to “The Duke of Argyll, 20 Ciarques St, London W, England” and redirected to Inveraray Castle, Argyll, with London W postmark on face (2 OC).

The Camp Borden FPO militia handstamp, although faint is a particularly scarce marking.

Reverse with Inveraray receiver (4 OC).

The Duke of Argyll, the 10th Duke of Argyll, Niall Campbell, servd from 1914 until 1949 upon his death. This seat was Inveraray Castle. He was also a honorary Colonel of the 15th (Canadian) Argyll Light Infantry.

https://en.wikipedia.org/wiki/Niall_Campbell,_10th_Duke_of_Argyll

https://en.wikipedia.org/wiki/Inveraray_Castle

A photograph of the duke of Argyll, sporting the trademark argyll socks can be found here. http://www.eccentricbliss.com/tag/10th-duke-of-argyll/