A housing contains a battery-operated alarm and a spring clip to hold a billfold to the housing. A plate is removably attached to the housing and functions to hold open a switch in the alarm's circuit. If a thief attempts to steal the billfold, the housing is separated from the plate, allowing the switch...http://www.google.ca/patents/US4090183?utm_source=gb-gplus-sharePatent US4090183 - Billfold anti-theft device
