Sir Charles, I would consider a Heiser holster for one of those quite a treasure, and I'm guessing it may have been made for the M1902 Colt, but will fit the M1903 Browning/M1907 Swede because as you said, they are quite similar. I would say the main difference is the Euro M1903 is blowback and the Colt M1902 is recoil operated, with dual swinging links at both the front and rear of the barrel.