hi dave
in all my years in this hobby i never seen a navy marked nambu pistol and i never seen nambu ammo with head stamps to identifi the nambu ammo only fraze used for years true its a bottled neck cartridge which it is the 7.63 broom stick mauser pistol ammo is close in size just a little longer but side by side its close call i can tell difference the only outher is the baby nambu pistol 7mm or the only outher is the type 26 revolver dont remember that calliber is it 9mm sorry im getting old and forgetfull on stuff like this hope you agree god bless andy the only military nut around