What Is This Relay For?

What I have in my 67 is something like this but homemade (piezo buzzer and a couple of diodes under heat shrink). Not much larger than the lollipop they give you at the bank. its high pitched beep isn't loud but right there at the fuse box so I do hear it. I built about 25 of them before I knew aftermarket offered something similar.
https://www.napaonline.com/en/p/NDP...MIzfTPl8D36gIVEb7ACh0TiQD5EAQYASABEgLQEfD_BwE
You could completely amputate that antique buzzard and its wiring. That black hot wire may not be fused. I don't have 69 wiring diagrams to confirm.
This replacement is attached at fused/line out side of 2 circuits at the fuse box.
One difference is it activates at ignition switch off if lights still on. The door jamb switches are not related.