What are these?

A central perk of Connecticut residency is shopping at the Big Y market. While this store delights me to no end, there is one mysterious aspect to the whole experience: these simple silver (yes, silver) coins larger and lighter than a quarter. I have now accumulated several of these over the course of my visits. They arrive once you surrender your money to the surly teenager manning the cash register and passing silent judgement on your combined purchase of yogurt, q-tips, and the latest edition of Weekly World News. Once your apparently pitiable items are paid for, the teenager says "Congratulations, you won a coin" in the most anesthetized voice possible. After which you are the proud owner of a new Big Y coin. After which you return home, stow your q-tips in their appropriate cabinet and suddenly wonder what the hell you are supposed to do with said coin. Stack them in a tower? Glue them together? Make a necklace out of them? Or perhaps they have a more sinister purpose. Could Big Y be attempting to bring down the Fort Knox with an alternative currency designed to supplant our beloved greenbacks? What does Alan Greenspan think about all of this? Of course, no Big Y employee has seen fit to explain what these things are good for, and thus their value seems infinitely arbitrary.

My obsession with this quirky store is not unique. Some poor soul has taken time out of their day to compose a Wikipedia article dedicated to the establishment, confirming my hypothesis that Wikipedia is 95% effluent. But at least the entry clued me in to the meaning of "Mad Mondays" at the store, which is apparently not when Bellevue patients staff the cheese counter, as I previously suspected.