This model of bayonet was originally made under contract for the British to fit the Pattern 1914 rifle. The bade is almost identical to the P1907 bayonet, as is the scabbard. The distance from the muzzle ring to the spine of the blade is different. The two vertical grooves in the grip is to make an easy distinction between this bayonet and the P1907. By the time the contract for P14 rifles was completed America was in the war and didn't have enough 1903 Springfields to arm the troops. Three factories were already tooled up to make the P14. It was easier to convert the P14 to 30-06 caliber than to retool for a different rifle. The redesigned P14 became the American Model of 1917 or M17. The same bayonet worked for both rifles. The scabbard throat was changed to include the wire hanger to fit US web gear. There were some parts left over from the British contract that had already been stamped with the British markings. These markings were lined out and the US markings applied. That's where the double marked ones come from. Once those parts were used up only the US markings were stamped, as in your bayonet. The P14s and M17s went into storage after WWI and were brought out in WWII to arm second line troops like the Home Guard, shipyard guards, training units etc.