What is this on back of speedometer?

[70dart318]

im hooking back up my speedometer. I bought the car with it not installed. And I see this on back. What is this and does this go anywhere when installing the instrument panel back up? Thanks

 

[TrailBeast]

That would be a condenser for the power through the gauge voltage regulator.
The tab goes in the slot along with one of the regulator legs.

I'll get you a picture.

 

[70dart318]

That's exactly what I needed to know. Thanks