Unmarked trigger housing....

[W5USMC]

Are you sure about that? - Bob

Yep,
"The hammer pin was designed to be inserted into the trigger housing from left to right. The width
of the "shelf" below the hammer pin on the left side of the trigger housing was designed for the
stock to hold the pin in place when the carbine is assembled."
The U.S. Caliber .30 Carbines - Trigger Housing Group