Interestingly enough, Beret that was "found" in Driel recently matches (minus the two rank stars ) the " Airborne headgear ' example of a Captain's Beret. And the one in the Book is a "relic of Arnhem" located at the Oosterbeek Museum. Only difference is where the grommets are located... 12 o'clock for the Lieutenant, and 2 o'clock for the Captain. Hmm..... ?????
Looks like two Polish Officers lost same kind of Beret in Arnhem somewhere, (same maker, different grommet position) and that would suggest that these types of berets were issued to Polish Paratroopers, however these are the only two examples that i am aware of and they have no provenance, other than "found" .... Found where ? the outhouse, at the river, local flea market ? and when ??
However there exist berets with provenance : I know Tony Z has one, I am fortunate to have one and Gary J has handled a few. All Gelfer.