One of the most lovely pieces of snark, and/or early example of an Easter egg on an album cover. This is TUBULAR BELLS by Mike Oldfield (1973), and faintly printed in the lower left corner we find:

“This stereo record cannot be played on old tin boxes no matter what they are fitted with. If you are in possession of such equipment please hand it in to the nearest police station.”

(I write this to put it on the web. If Google is to be believed, no one else has written about it.)