Abstract: A security system for use with a coin container and a coin-processing machine having improved tamper-proof features. The system includes key means in a machine housing which engages with lock means associated with the container. Relative rotation of the lock with respect to the key positively locks the container, to protect coins in the container from pilferage. High-strength mounting means join the key stem to the housing so that the key stem is firmly fixed from rotation which would otherwise override the security of the system.