An antenna assembly for use with a level measurement device for measuring the level of a material held in a container is provided. On the cathode formed by the surface of the capacitor element, a conductive adhesive layer containing silver particles and an organic silane layer made from aminopropyltriethoxysilane are sequentially formed, and the cathode and a cathode terminal are connected through the conductive adhesive layer and the organic silane layer. The vending machine receives a proof-of-purchase identifier, and has a processor configured to permit at least one of the items in the machine to be dispensed for less than the predetermined price if the POP identifier was received.