Mystery of the Coins

I was cutting seats the other day while listening to David Attenborough and all of a sudden three coins fell out of the seat. Someone had deliberately sewn them, in a straight line, into the lining of the seat - the interesting thing was that there was one coin from each place in the Pearl River Delta area - 1 Macanese Pataca, 1 Hong Kong Dollar and 1 RMB. Can anyone explain?