In last weeks episode of Life on Mars, there was reference to a ‘Party Seven’ being the stake in a bet.
Also, I was looking at this thread last week and a few of the posts mention the rarity of finding one, particularly an unopened one.
Didn’t bother me at the time (or I would have taken notice to the details instead of just watching the show), but it does now and I want to know! Google doesn’t show up anything, 'cause I’ve got no real idea of any other words to put into the search string!
It was beer (usually bitter) in a big can; cheap and usually of dubious quality; difficult to open (the referenced show had them attempting it with hammers and screwdrivers) and the beer would most often be warm, because this was an item people would buy on the way to a party (or would just forget to refrigerate).