Regarding the original question of this thread, there was no mechanical changes in Parker guns after 1917 or so. The 1910 change was the reduction of parts in the top lever mechanism and also the patented stepped wear plate. And then around 1917 the top lever spring went from a flat type to a coil spring/plunger type.
The "18-4" thing you mentioned was a prototype gun that James Hayes was working on and those design changes were never implemented ito production. For more information on this, I would suggest you read my article in the Summer 2013 issue of DGJ.
The only other change around 1917 was the style of the safety button, and the shortening of the top lever. The style of the safety button spring and safety jacket also changed some at this time. But I would not consider these to be actual "mechanical" changes.
__________________
B. Dudley
|