Abstract: Apparatus and methods for securely monitoring the sales transactions in bulk vending machines are disclosed, the apparatus operable with at least one bulk vending machine having a coin mechanism that conventionally includes a coin plate, a selectively rotatable handle having a shaft extending radially therefrom, and a coin shuttle. The apparatus of this invention includes a lobe bearing cam mountable at the shaft and an adapter/sensor having first and second switches and an output interface mounted thereon, the switches oriented relative to one another so that the maximum amount of normal backlash (reverse rotation) of the coin plate during vending is accommodated (is less than the angular spread between the switches). The apparatus further includes a microprocessor connectable with the switches through the output interface for counting and recording sales indicated by activation of both of the switches in order, and circuitry for identifying occurrences of apparatus tampering or fault.