. . . since the abdication of Edward VIII, the abdication notice was signed December 10th 1936 and the abdication speech to the nation made on December 11th. Here's the wiki link.
The postcard shows a young Prince of Wales, and is published by Valentines. I had intended to post a photo of an Edward VIII coronation mug, but alas it is as I type still 'unlocated', although I did find a bunch of postcards which I'd misplaced, whilst I was looking.