Just a note for those who like technical details...
The "Checkering" and also the "splines" or straight lines on the second cap example are impressed on these parts by a process known as "Knurling" The target piece is rotated and pressed under HARD pressure against a movable device that contains two or more rollers with the opposite impressions made in much harder material... It is the same process that is often used to make similar impression on cylindrical metal tool handles... The process is generally accomplished in a lathe. Pressure is applied until the impressions on the target piece are made to a satisfactory depth.
My late friend and gunsmith John Dusing used to make his custom gun screwdriver handles this way out of aluminum or steel rod. Anytime John found a screw for which he did not have a screwdriver that fit PERFECTLY, he would grab an appropriate piece of drill rod and make the screwdriver complete with a fine knurled metal handle... He passed away around 1983... I sure miss that guy and the stories he used to tell
