Picked this up at SLICS (available in quantity), 20 x 102mm dummy, only markings are on the projectile: GLN14A852-002 20MM. GLN = Galion Inc., Galion, Ohio, 14 = 2014.
Projectile body is magnetic, dummy nose fuze is nonmagnetic.
In the cartridge base is what appears to be a large button head screw which is nonmagnetic (stainless steel?), the hex slot is filled with what appears to be grey epoxy.
Cartridge case is brass.