I have recently found some of the US Insignia incorrectly dated and not based on the hallmarks on the back of the insignia. String in the Korean War era the US started using assigned hallmarks. 3 digit numbers were issued during Korea by the US Marine Corp to ID manufacuers. Also during the Korea War ear the mark "GI" appeared on a number of item. But in 1953-54 everything changed when the US started to require a number followed by a single or two digit number. This ID the time frame and the manufactuer. This changed in 1964-65 when the system still in use today came into being where the system changed to a Letter followed by a 2 digit number.
