Phantom Corsair Perfomometer
 

At least I think it's a Performometer.

https://blogger.googleusercontent.co.../s640/fbdf.bmp
justacarguy.blogspot.com/2009/03/1938-phantom-corsair.html

Here's a screenshot from a Youtube video:

https://ecomodder.com/forum/member-f...formometer.png

Click to enlarge. The triangular orange mass damper covers the name so 'performometer' is speculative.

Does anyone have a user's guide to that instrument?

' gauge '
 

For that time frame, I can't think of any available technology other than a manifold vacuum gauge that you could buy from Pep Boys, that had a custom dial face, which implied recommended throttle use, depending upon a specific performance interest.
The '61 Dodge that was my grandfather's has one, and without some form of restrictor / dampener, it's pretty much 'useless', as the needle swings widely, all over the place, even under really small accelerator pedal movement.:o

Vacuum gauge was my first thought too; but expand the 2nd pic and look at the various scales -- 0-40-0 on the outer ring, pulling power 0-700 over half sweep on the second ring, the third ring shares 'tractive and wind resistance lb/ton' and 'acceleration % of G'.

How the h-e-double hockey sticks do you get stopping distance from a vacuum gauge? And there appears to be a needle stop at the 9 o'clock position. There's no way to select functions.

I'll be watching for one at swap meets. :)

Unless it has a source switching scheme, those different scales have to be interdependent. Rules of thumb so to speak. Not fluent in the use of a vacuum gauge for economy, understood the theory not the practice. Do know the system vacuum drops like a rock when applying brake in kinda a linear fashion to stopping force, but that's theory not experienced. Hate vacuum brakes, no pedal feel. Long throw mechanical you can sense the point where the tires are about to skid.

' swap meets '
 

While you're looking, and asking around, see if anybody has a line on a 'Tapley Meter'.
Road & Track used this device in the 1950s ( created by the insurance industry to quantify automotive brake 'deceleration rates' ) which R&D reverse-engineered the data for 'performance' acceleration testing, coastdowns.