Posted 27 April 2012 - 12:53 PM
The short answer is yes, they did. I have come across a couple, one to the Second Mate of a vessel sunk in the North Sea, and the other to a Stewardess on the Leinster which was torpedoed between Holyhead and Dublin in October 1918. Williamson's recent book on collecting WW1 medals shows a picture of the printed King's condolence slip accompanying Merc. Marine Memorial Plaques.
The longer answer is less certain: for CWGC commemoration the Mercantile Marine casualties were usually only officially recognised if death was the direct result of enemy action and they were on duty at the time. If they fell overboard in a storm or sank after being rammed by an Allied ship that probably didn't count! The other problem was in the issue of medals etc. - the Merc. Marine war medals had to be applied for by the next of kin and weren't sent automatically. So maybe the casualty had to be both officially recognised AND their families had to make a claim for the Plaque? I'm not certain whether the Merc. Marine were entitled to the Scroll of Honour either.
Hope someone else can amplify this for you!