Hard to see but it looks like there is a grove on the inside of the hammer .On the striker there was an extension with a peg that located in the grove .Mine was trial and error and took a lot of bad language to get it right as I had no pattern to copy .It is no wonder that Pape abandoned the idea as it dose have IMHO built in complications and weakness .
As to drawings I would doubt if there are any in existence and I would hazard a guess that the originals were little more than a sketch.