Anyone Know What This is?

[rcprace]

My son and I are so close to finishing his '74 Charger, but we've run into a few questions that we can't seem to find answers for.

First - Does anyone know what the circled item in the photo is, and what it does?  We've checked several different wiring diagrams and can't seem to figure it out.

Second - We bought a wiring harness from Year One about 15 years ago that we've just finished installing.  It's one for the engine electronics (Cluster of 17-24).  There a couple of wires that we're not sure of, and we're hoping someone may have a list of which wire ends plug into what equipment.

Any help would be appreciated 

[b5blue]

I think it may be the seatbelt interlock for the drivers seat. 

[Nacho-RT74]

seatbelt device is the one with red button... which is a reset button

I think is a NOSX device related ( emision controls )