This style of Gougler master key was entirely unique to Gougler. Very early ones appear to have been made from brass and cut, later ones look like stamped sheet steel. There was a little discussion of these here:
http://www.antique-locks.com/showthread.php/2192-Gougler-keyless-padlock-combination
See August 2, 2013 03:26 for some images.
Some other images of Gougler keys:
Here is what a sample lock looks like with the back removed:
I expect there were not too many distinct keys, maybe 10-20. They seem to be very rare. I sometimes describe them as warded keys but operating in polar coordinates. They key is inserted then pushed sideways which rotates the “stem” seen in the above image. The 2013 images show this well.
