Way back in the dark ages (1973) I worked at Rohr Industries in Chula Vista, CA as a computer programmer. Rohr made large components for jet engines (among other things) and so my work site was in the factory. I thought it strange that every day all the factory workers had to open their lunch pails to show that they weren't carrying out anything belonging to the company, but I was never asked to open my briefcase, which could have contained a mag tape with all sorts of sensitive, proprietary company information.