Abstract: An electronic coin tracker for coin-operated machines, particularly video games, is retrofittable to most such coin-operated machines as produce an electrical signal upon the deposit of coins. The coin tracker is physically and electronically secure in its function to monitor both (i) the deposit of coins and (ii) the activity of the coin operated machine (whether such activity is responsive to, or only to, the deposit of coins or not). The coin tracker reports the monitored (i) coin deposits and (ii) machine activity electronically, preferably through an infrared light data link. The reported data may readily be analyzed to determine whether or not the machine operation and/or machine receipts have been subject to fraud or embezzlement.