3877155

Information

• Patent Grant
• 3877155

• References
• Source

• Patent Number

  3,877,155

• Date Filed

  Not available

• Date Issued

  Tuesday, April 15, 1975
  50 years ago

• CPC

  • G03G15/22 - involving the combination of more than one step according to groups G03G13/02 - G03G13/20
  • G06K17/0032 - Apparatus for automatic testing and analysing marked record carriers, used for examinations of the multiple choice answer type
  • G09B3/085 - with invisibly printed correct answer; the answer being rendered visible by special optical means

• US Classifications

  • 434 - Education and demonstration