I'm following in the footsteps of others who've been copying ad pages from other issues, and who've shown that issues of Jungle have the same ads as Jumbos+10 [Jungle38=Jumbo48, etc].
However, I do some checking each time near the issue I'm upping, so this time I checked available issues between 37&40/47&50, and indeed all ads are the same.
Of course, this isn't 100% proof (delicious!), but I believe it's close enough.