 The K & E 4081-3 Log-Log Duplex Decitrig was a mainstay for engineering students and practicing engineers in the 1940s, 50s, and 60s.During World War II, the company made fire-control instruments for the US government and won seven Army-Navy "E" Awards for Excellence in Production.With the advent of the electronic, transistorized calculator in the 1970s, slide rules became obsolete for most uses.