Released in 2000 in response to the growing number of altered Chinese
coins and circular
pieces of metal
used to rip off vending machines
and train ticket
machines. These new coins have special features that can help the vending machine differentiate between the real things and the fakes which were altered to be the same size and shape of the real 500 yen coin.
For a period, 500 yen coins could not be used at hardly any vending machines in big cities because of the owners' fear of getting ripped off. I can't count the number of times I had to break a 1,000 or 5,000 yen note because a few people decided to screw up everything for the rest of us over 500 yen.
However, the plan to beat the cheaters backfired. Within weeks, the bad guys found ways to get around the new coin and vending machines mechanisms. So we are back to square 1. Can't use the new or old coin in any vending machine because the owners feel no need to switch or upgrade their machines. I am relieved that at least we can use the old coin at train ticket machines, but the new coin cannot be used at vending machines.
Thanks to the boyz in Nagatachou and Kasumigaseki for getting on top of this one!
UPDATE (8/19/2002): Now a few years after, there still is some trouble. Most machines will accept Y500 coins, but are picky and will accept either old ones or new ones, not both. JR will usuall accept both, but places like Matsuya will only take the old ones.