The first series were made between 1939 and 1945. Most people call them "Pre-War Tech". I don't agree with the timing, as World War II started a year after the patent application was filed and a few months after the technology was put into production. Actually means "before America went to war"... but that term is incorrect in my opinion, since World War II actually started in 1939. Private opinion. I came across this idea on one of the forums and agreed with it. If I'm wrong, please correct me. I was just interested in how to properly attribute them according to the era.