A ACVW nut.?
 

If I go to a bug in/ meet. I take along the "nut" that you used to find
behind the dash. it held the light switch in.
It was made out of brass. I polish it and ask people if they can
identify it.. I usually have along a complete switch to show where the
"nut" came from.
the "q" is why brass?
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Karma ; what a concept!