'PW' (ii) was the designation of Allied convoys (together with a numerical suffix) plying the route from Portsmouth to Wales, and as such reciprocals of the 'WP' series (July 1941/June 1944).
The first of these convoys was PW.2 of 9/10 July 1941 with the 3,357-ton Dutch Santonia and three British vessels in the form of the 1,507-ton British Scout, 6,907-ton Cavina and 5,249-ton Empire Progress, and the last was PW.530 of 31 May/2 June 1944 with the 5,417-ton French PLM-21 and 7,321-ton Norwegian Vinga among a total of 19 vessels.