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3281821
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Patent number 3,281,821
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Issue date Oct 25, 1966
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H04 - ELECTRIC COMMUNICATION TECHNIQUE
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3245074
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Patent number 3,245,074
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Issue date Apr 5, 1966
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G09 - EDUCATION CRYPTOGRAPHY DISPLAY ADVERTISING SEALS
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2815448
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Patent number 2,815,448
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Issue date Dec 3, 1957
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G01 - MEASURING TESTING
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2725549
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Patent number 2,725,549
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Issue date Nov 29, 1955
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H04 - ELECTRIC COMMUNICATION TECHNIQUE
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2398677
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Patent number 2,398,677
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Issue date Apr 16, 1946
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H04 - ELECTRIC COMMUNICATION TECHNIQUE
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2350146
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Patent number 2,350,146
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Issue date May 30, 1944
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H04 - ELECTRIC COMMUNICATION TECHNIQUE