Just to set this straight for you incase. A
coindoor is the metal plate you put on the front of your machine. It can be just for looks or it can be functional. To be functional, you require
coin mechs. Coin mechs are the tall skinny electronic things that you snap into the back of your coin door so that when coins go through the slot, they go into the mech to be processed. When a coin is right, it flicks a switch (which is the part hooked up to the iPac) and then drops the coin out the bottom of the mech, which is where people put
coin boxes to hold all the coins. The coin box is just a piece of metal formed into a box where your coins get stored. You could probably use a large funnel and a tin can for the same thing, and you get the authentic sound

Hope that cleared it up for ya.
EDIT: BTW, you're not looking for one thing. If you just want looks, you can use a coin door alone, but for a coin operated game, you need at least the coindoor and coinmechs. The coin box can be easily built out of household things, even if you have a spare baking pan! Sometimes, people put doors and wire it up so when you smack the door or press the coin return it will send a coin signal to the iPac, which would be considerred using it for looks.