Those capacitors are likely there to keep the meter from "bouncing" since generator outputs can fluctuate so much. The capacitors just act as shock absorbers to keep the meter's needle steady so that an "approximate" voltage reading can be obtained.
Yeah Ed,
These capacitors are also known as "smoothing capacitors".
I've seen these used here a few times in dairy sheds, the capacitors need to be sized correctly, or it will throw the meter readings out of wack.
