Does the Miniature Vending Machine do anything aside from being shiny and temping?

You can open it and obtain 3 random old Donation items.:D

Yes you'll get 3 random Donation Items, but you can always get low priced items, so you are taking a risk. You can get Donation Items, Donation Presents (unopened ones) and even a Miniature Vending Machine out of it xD But as I said, some items are not pretty expensive...