Prototype 1 - Converging lines in sterling silver

 

 

 

 

 

Close-up of the barrel end

 

Close-up of the cap

No production 75 I know has a pattern similar to this, with the converging groups of lines that appears on both the cap and barrel.  

When I saw a Parker 51 model with this exact pattern on its cap (the barrel was in plastic), I wrote to Parker historian and expert L. Michael Fultz who responded as follows:

"In the Parker 51 it was called Converging Lines and was done on a Gorton engraving machine using a diamond burnisher rather than a conventional cutter. ... I have never seen this pattern applied to a 75."

Here is a picture of my friend's Parker 51 with a close-up of the cap.