Unpowered mechanical gate opener, part 2

Now here’s a perfect example of why I love the MAKE community. In response to my earlier post about the possibility of modern mechanical gate openers, reader MichaelLubke went out and took these photos (1,2,3) of a real live working mechanical gate near his ranch. What’s more, he ran down the original patent on the gate’s design! This patent, US number 3,163,947, was issued to Mr. Alvin E. Gandy of Eden, TX, in the year of Our Lord nineteen-hundred and sixty-five. His invention, known as the “Gandy Slide-A-Way,” is activated by the weight of one of your vehicle’s tires on a short steel ramp built into the driveway right in front of the gate. I wonder how many of these were ever made?