Slurpee Button Gallery

Some flavors that I've seen referenced in print from the same time frame might have had buttons issued for them but I've never seen them: "Cold, Green and Wet" and "Fire Water." Of course, there may be others. One interesting item is the "Mad, Mad Slurp' button. The RC Cola advertising campaign back in 1967 (see the RC Cola Button Gallery" had the tag line "Royal Crown Cola with the Mad, Mad Taste." Coincidence? Note that many of these have a maker's seal with the number 241-L stamped in tiny letters along the edge of the button. Anyone know what this means?