A while ago I posted about the Tapley meter. I was surprised and delighted to be given another similar device from another manufacturer. This is the Burg Dynometer. Complete with instruction leaflet. It works in a similar way to the Tapley, but is smaller. I was told someone wrote "keep off" on the box in 1979, so it could be no one touched this meter since 1979.
A good view of the dial despite the air bubble. The meter can be mounted to the windscreen with a suction cup and should be mounted so the hand is at the 0 position then you adjust the yellow indicator near the hand. Then you can drive the car and accellerate or decellerate and the hand will move the in dicator so you can read deceleration or acceleration force.