The Jackson Electrical Instrument Company was founded in Dayton, Ohio in 1933. The founder, Paul Jackson, died in 1957, and in 1966 Jackson E.I. mowed to Mineola, New York when it becomed a division of their competitor Mercury Electronics. As division of Mercury Electronics Jackson faded away in early 1970s. Their most notable product was 648 series tube tester of wich 40000 units where made in diferent variants. The Jackson E.I. was also one of rare manufacturers who offered low cost kit upgrades for modernization of their older instruments and bringing them up to date. Source: Jackson model 648 complete manual by James Cross, Vacuum Tubes Inc.