Here's a mystery: I was watching a Smiths concert on TV last night, recorded for German TV institution Rockpalast in 1984. As Morrissey and Marr were followed back to their dressing room, I spotted the above Beastie Boys sticker on the dressing room door.
As we all know, the Beasties didn't get anywhere near the mainstream until the build up and release of Licenced To Ill in 1986 - and research shows that they didn't appear on Rockpalast until 1998. A quick Google brought up the video below of them from 1984 (not from Rockpalast, from the Scott and Gary Show), so they were on the radar to some extent and Ad Rock even seems to have a similar sticker stuck on the front of his guitar.
Add your suggested explanation in the comments.