Grandpa worked heat treat at the alegany national forge, where they made stuff like the beams for the empire state building, periscope tubes, and the 16" guns for the biggest battle ships, each thing had to be tempered in a very specific way, and to deal with spying and espionage, the charts and instuments used on the shop floor were all deliberatly wrong,and the written instructions were also wrong leaving the person in charge to know how to convert the given instructions into what was actualy done through a secret method, not complicated, but essentialy impossible to reverse engineer. There is a story of soviet engineers who somehow were invited to tour the RR jet turbine factory, and were given shoes that had extra sticky soles they wore only for the tour, which ewere then used to anyalise the metal chips that get picked up from the shop floor..... never ends, expected.....even honored