I'm in the process of recording my grandpa talking about his life. He actually doesn't say much about the bottom of the can. Basically that he went back to his shop and sketched out some ideas based on the technical specs he knew they needed, and just kept building prototypes until it worked. I'm going to try and get him to tell me more about it this weekend. Here's a short recording of him talking about a fix he did for the military: https://soundcloud.com/jscheel/frank-scheel-ammunition-work