back in 2008 I came across the next one made (according to the serial number tags, which crazy, we both photographed)
http://justacarguy.blogspot.com/2008/11/rare-historical-automotive-jem.html and the follow up gallery
Notice how the first and second black and white photo are the same car as this color photo I took of a Coney Island bumper car, just a small bumper addition difference

I think I've posted all three of these photos (found on http://www.atomicantiques.com/) before but seperately, not realizing that they were Custer Cars 
For the new photos I just took in Jan 09, far better photos, http://justacarguy.blogspot.com/2009/01/custer-chair-update-1941-engine-powered.html

The back tires are 20 x 2", United States Rubber Company... and look as old as the car!
Advertisement from the Roosevelt Warm Springs Institute via: http://www.disabilitymuseum.org/lib/stills/1122.htm

The above 3 photos are of a Custer bumper car in the collection of Only Yesterday, it may be gas or electric, I don't know... but is really similar to the car in the photos that Hemmings picked up on http://www.shorpy.com/ and ran a bio and story about other models the Custer Specialty Co made. http://blog.hemmings.com/index.php/2007/12/18/early-alternative-fuel-vehicle/