We had to use coins in our last game.
We started out with a 600 IPC budget for each power, so the number of units on the board was pretty big.
We used all of the regular chips, and then used pennies to represent a red chip for USA, UK, Russia and Germany and Japan had pennies for grey chips (complex, but we didn't have much change at the time).
We did have to use silver coins as grey for other powers as well, at one point USA had WAY too much Navy
Hopefully I'll be getting another copy of the game to compliment my buddies copy so we'll have lots of chips