Well, I decided to get serious and do a Google search for Willies - at first I thought that since they were images, and advertisements, they wouldn't show up in a text search, but I was wrong. So here is what I learned:
There are a total of 22 unique ads
The first appearance of Willie was November 25, 1939 - but he was unnamed
The first named appearance was January 20, 1940
The last appearance (as far as I can tell) was July 25, 1964.
Some years there were no appearances of Willie at all - although I'm not sure how reliable a text search is - I found an ad in a 1961 issue, but the search did not find it.
I've posted seven of the Willie ads so far - I will post the rest over the next few weeks.
Here's a lingo-packed ad:
We all know what "a wack of the rum keg" is. It looks like Willie is in cahoots with the ship's cook - no doubt another rapscallion.