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Class Information
Number: 434/328
Name: Education and demonstration > Question or problem eliciting response > Correctness of response indicated to examine by self-operating or examinee actuated means > Involving heat or chemical reaction
Description: Subject matter wherein the correctness of the examinee"s response is revealed by means of thermal energy or a chemical transformation.

Patents under this class:

Patent Number Title Of Patent Date Issued
6879805 Test form having a removable opaque layer, and method and apparatus for printing on the form Apr. 12, 2005
6152449 Combined sticker and invisible ink game Nov. 28, 2000
5217231 Power of observation invisible ink game Jun. 8, 1993
5188871 Authenticatable security paper Feb. 23, 1993
5160266 Mix and match invisible ink game Nov. 3, 1992
5011445 Color memory toy set Apr. 30, 1991
4787852 Multicolor interactive notepad Nov. 29, 1988
4781595 Visual design and character formation composite Nov. 1, 1988
4744113 Toilet training aid and method May. 17, 1988
4702497 Method of encoding a symbol or message on a plastic material and an article on which a symbol has been so encoded Oct. 27, 1987
4631203 Latent imaging and developer system Dec. 23, 1986
4514177 Invisible ink quiz game Apr. 30, 1985
4360548 Self-contained covert image Nov. 23, 1982
4337051 Self-scoring test with non-disclosed key Jun. 29, 1982
4198445 Latent image printing and development Apr. 15, 1980
4188431 Latent image printing and development Feb. 12, 1980
4139965 Device using coated paper and chemical reactive marker Feb. 20, 1979
4111462 Latent, sensitizing ink Sep. 5, 1978
4084332 System for visual communication Apr. 18, 1978
4051283 Printed sheets containing concealed images and method and materials for preparation and visual development of same Sep. 27, 1977
4038761 Element and method for teaching with liquid crystals Aug. 2, 1977
4028118 Thermochromic materials Jun. 7, 1977
3990156 Constructed response method with invisible answer indicator to prevent cheating Nov. 9, 1976
3979550 Pre-printed latent image spirit duplicating masters Sep. 7, 1976

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