[usmc1988]

Found these in a box of Browning parts. One is marked "WW" and the other is "S" marked.

 

[ajmdreammg42]

I think they are "filler plugs" for a m2hb back plate for a fixed position gun.

 

[glassmountains]

AJM is correct. The block fills the hole where the trigger and bolt latch release protrude through the top of the backplate. All M2's that were solenoid or side trigger fired had these installed. They were either a solid block or a stamped out piece.