I found an Iron Special Coin during a random event and I'm not sure what to do with it other than chuck into my vault. Can someone please tell me what I'm supposed to do with it?

You can use it in the coin machine (located in Centropolis) in exchange for a prize.

Alternatively, you are more than welcome to just sell it in your shop.

are they good prizes? Or are they random like the vending machines?

I think "good" is a bit subjective, haha, but there's nothing in there that would knock your socks off or make you rich. The coin-machine exclusive items are mostly worth around 25k, but some of them are cute so maybe you'd think they were good, 'ya know? It also has a chance of giving a random pet a random stat, giving a small amount of sP, or spitting out a random restockable item.

that's good to know, there's so much going on with the site and I'm always learning something new! Thanks for being super and sharing :D

You're very welcome! ^_^

This is perfect as I was also wondering what to do with the coins! Thanks Magic and thanks Priscawippa for making this topic hehe