CARNIVAL MIRRORS DETAILS:
These were typically prizes for carnival games - and are simply stickers that were laminated onto the bottom of sheets of glass. Interestingly enough, both the ones in my collection as well as every image I've seen online, all the mirrors featured exclusively 3rd Series characters. This puts the manufacturing date of these plates around early 1986 (since Original Series 3 was released in January, 1986).
The edges are very sharp so they were inserted into the cheap cardboard frames for protection. In fact it is possible to hear these referred to as 'Garbage Pail Kids Glass' as opposed to mirrors. These are 'bootleg' items that were never officially licensed - very rare!