I picked up a freeby '51 Chevy the other day for parts and while looking it over I noticed an odd choke knob.
http://i891.photobucket.com/albums/ac112/Twotone_photos/IMGP3503.jpg
It works like your regular choke knob, but when you push on it, it snaps into place tight against the dash. Anyone know if this is after market or just original to another vehicle?