ICS Original part MP-42
ICS brand MP5 Lower receiver / grip with Navy Trigger Group
Commonly used for the GSG-16 modifications (.22 Cal Rifle) as seen here:
https://www.ar15.com/forums/Armory/GSG-Mods-Firing-Pin-Mags-Buffer-Stop-Screw-Replacement-Fake-Can-Laser-Lowers/41-244302/?page=1#i2122589