I am pretty sure I have one of each of these and I have no idea what they're for, anyone know? Or should I just sell them?

They can be used in the Coin Machine but I believe what you get for them is random. You can probably get more for selling them, I'm not sure how likely you are to actually profit off of them.

Thank you :)

If it helps, I've gotten a couple during the past few days and decided to try them out as a gamble. I got a 3K item from one coin that was selling for 125K, 5K from a 100K coin, and I can't remember what I got from the other coin, which was a 125K coin.

So I'd say you're most likely better off selling it.

I had been donating a few. lol