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SELECT DISTINCT patent.*, YEAR(date) as year FROM patent LEFT JOIN category ON category.patent = patent.patent AND category.type = patent.type WHERE (category.class = '451') AND (category.subclass = '239') ORDER BY date ASC, patent, type

Total of 1 patents found where: Class is '451'; Subclass is '239';

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T / S Patent Date Description Patentee Category Assigned To
U 1,186,203 June 6, 1916 Apparatus for Use in Manufacturing Articles of Ceramic Material
Method of manufacturing spark plugs
JEFFERY, Joseph A.
JEFFERY, Benjamin A.

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