Just out of curiosity, how much corn do you put in a corn door? (the subject... nevermind)
Anyway, if you could take one of the switches off and get a good look at it it might be labeled (as suggested above).
If you don't want to get a multimeter, you could always run the ground to one pole (call it pole X), and wire pole Y to the coin 1 terminal on the i-pac 2. Then open a text editor on your computer and see if you get a 5 when you trip the wire trigger on your switch. If not, try the other open pole (Z), and finally try Y and Z. If none of them work, order new coin switches from Happs, which are labeled.
It doesn't matter which pole on the switch is technically the "C" and which the "NO," as long as the circuit is normally open.