Original North Vietnamese Vietnam War Army Boonie Hat with Waterproofed Crown - Size 56 Ammunition and the front sling swivel

and the  front sling swivel is also missing

which may be more recent replacements

but also the Imperial Japanese Army and Navy (who captured them from the Dutch)

The markings on the barrel are:

Original North Vietnamese Vietnam War Army Boonie Hat with Waterproofed Crown - Size 56 Ammunition and the front sling swivelOriginal Item. Only One Available. This is a scarce North Vietnamese Boonie hat as worn by the NVA during the Vietnam War against the United States. This example is stamped Size 56. These are very scarce and are a very iconic piece of NVA headgear. The hat is in good shape with a waterproofed crown, which is distinctive for use by the NVA. These were prized souvenirs for GIs serving in country during the Vietnam War, for those who were lucky enough to