I've had this map case for a number of years and just found it again. It was from the estate of a US Army officer who entered the army prior to WWII and then was commissioned in WWII and went on to serve in Korea and Vietnam. It doesn't seem to match any of the WWI or WWII US Army map cases that I've seen over the years and I see no indication of any maker's marks. Does anyone know if it's GI Issue? If so, from when?