from what I've learned, they were stock on Ruxtons... and an add on to everything else, but common on DuPonts
Auburn Cabin Speedster
Above and below, DuPonts
Packard
1926 Rickenbacher
In the El Segundo Driving Museum, a Packard boat tail speedster http://justacarguy.blogspot.com/2012/05/packard-speedster-runabout-in-el.html
A hot rod I found at the Grand National Roadster show 2012
Yup, a Greyhound bus!
Cord above, and the rest are Ruxtons