Parker arrow clip, ...was never patented.
There were many others using arrow clips in and around the time Parker started....and in Europe also.
Hero is now making a Safari clone in China now that the patent for the Safari expired. The 'patent' for the P-51 or P-45 is also long gone....
Many pen companies made fake P-51's with out the massive collector in German, France and Italy right after the war.
The Italians were heavy into that...and Parker had the Army make sure no GI left Italy with a counterfeit Parker -51 in his dufflebag.
1928-9 Parker bought up Osmia to make the Duofold in Germany.....unfortunately there were many clones for lots cheaper...so Osmia got a free technology transfer as Parker couldn't sell enough Duofolds and sold Omsia back to the original owners by 1929/30. Lamy was the director at the time of Parker Germany.
I have seen either pictures or pens with an Arrow clip, that were not Parker.
German vintage '50-70 semi-flex stubs and those in oblique give the real thing in On Demand line variation. Modern Oblique is a waste of money for a shadow of line variation. Being too lazy to Hunt for affordable vintage oblique pens, lets you 'hunt' for line variation instead of having it.
www.nibs.com/blog/nibster-writes/nibs-germany & https://www.peter-bo...cts/nib-systems,
The cheapest lessons are from those who learned expensive lessons. Ignorance is best for learning expensive lessons.