A financial transaction card is transparent or translucent to human viewing yet detectable by automated card processing equipment. The card includes a substantially planar material sheet having upper and lower surfaces bounded by a continuous peripheral edge. The material sheet has one or more areas...http://www.google.co.uk/patents/US6296188?utm_source=gb-gplus-sharePatent US6296188 - Transparent/translucent financial transaction card including an infrared light filter
