Help ID'ing this silver thing

[88Ironduke]

The subject is a 72' Fleet side with 3OTT / I-6. The engine side of the wire harness was pretty beat up so I ordered a new harness from a local vendor on the forum. I got a new harness as advertised but I have to reuse some of the original for charging and headlights...

My dilemma is this little silver relay box and the section of wire it resides with. It bolts up on the drivers side fire wall outboard of the master cylinder. I have tracked it back to the bulkhead head connector via a brown/white strip wire that goes to what I would consider pin 1 of the engine harness next to a large purple wire. I just can't find that particular wire on the schematics. I'm having trouble uploading so any help is appreciated.

I am totally lost as to what this little thing is or does but I assume it is staring me in the face. Ideas and opinions welcomed.

88Ironduke