Tougher than the discs are the advertising for them. I have two pieces, both from sets issued near where I lived.
The Chillee Willee one is a mobile with a large disc shaped ad and three of the discs hanging below it from strings. It hung above the machine, and eventually got some syrup on a couple of the discs. I don't recall if I restored mine using extras I had or if I left it with the stains and all.
The Papa Ginos discs were advertised with a cardstock register display and a larger one that went up on the menu. I'd asked if I could get one when the promotion was over but they said the front office wanted them all back. A week or two after the cards were gone I spotted one down behind the register. Asked and after a bit of confusion they gave it to me. "hey, can I have that old ad with the cards" What old ad" "That one right there" " Confused look, where?" "down behind the register" Looks behind, pulls it out hesitates and finally says "sure here. "
That was a moderately tough set, one or two per purchase, and until right at the end even the kids in my school that worked there couldn't get me any or they'd be fired. The last week of the cards my family was at one at a mall a little farther from home and I got a duplicate. I tried asking if I could swap it for one I needed which hadn't been allowed in the past, and instead they brought out the whole bucket full, left it at the table and told me to take what I needed. Set complete!
Steve B