Patents Assigned to Earl L. Koppen
  • Tamperproof reusable bingo card
    Patent number: 4483538
    Abstract: A translucent intermediate sheet having a standard array of bingo numbers is sandwiched between transparent top and bottom sheets. Alterations to the card, such as by a cheater, to permit changing, adding or rearranging bingo numbers can be seen through the sheets.
    Type: Grant
    Filed: March 15, 1983
    Date of Patent: November 20, 1984
    Assignee: Earl L. Koppen
    Inventors: Earl L. Koppen, Douglas E. Winters