What is this?

[Yadkin]

On a 1974, two pictures shown, the low resolution prior to disassembly. This is the center of the instrument panel, the upper rectangle. What is it?
Second picture is disassembled, higher resolution.

[klweimer]

Maybe the dimmer control for the dash lights? The original rheostat had a tendency to fail and a lot of people just jumpered around it. I did.
Kirk

[Yadkin]

Thanks. I'll test it to see if it works before cutting holes in my new dash. I'll be able to get a round one to replace it very easy.

[Dawgme85]

That's the dimmer for the console lights, iirc. The dash lights are dimmed using the small rotary knob.

[Yadkin]

Oh gosh, what rotary knob? There are two black rotary switches in the center of the dash- I thought the one on the left was to turn the wipers on, and the right to change wiper delay. The only other roary is mechanical, near the speedometer, to reset the trip odometer.

[Dawgme85]

The windshield wiper switch is the right hand stalk on the steering column. One click down is for intermittent, two clicks down is for normal operation. The left hand rotary switch in the center of the dash controls wiper speed and the right hand rotary switch is the dash light dimmer. The horizontal rotary rheostat that was originally asked about controls the "ideogram illumination intensity", which are the heater control lights in the console.
Fiber optics are used to illuminate the heater controls.

[Yadkin]

Wow that's awesome. Thanks for the explanation.

[Dawgme85]

No problem. BTW, when switched to intermittent, the wipers operate normally for 3-4 swipes before finally switching to intermittent.