They may have been in Englandat one point and swapped with the Special Air Service chaps who knows.
Jim is correct the F/S knives are much sought after & not cheap I can vouch for that.
I sent detailed pics to Roy Shadbolt of mine, it's a 3rd pattern late or post war F/S that was exported hence the England stamping Roy is considered an expert collector and dealer in the F/S knife world.
I also have 1st Ed of Fairbairns All In Fighting where he shows how and where to disable the enemy with the F/S knife, expected time till they expire obviously the throat and heart are pretty much instantaneous.
The other book I have of his is 1st Ed Get Tough.