This is a knife/sword bayonet manufactured beginning 1917 and was used on several firearms to WWII.
They are very similar to their predecessors: the British P1907 (muzzle-ring is closer to the blade rib and does not have U.S. markings) and the US/British Model 1913/17 (has the same dimensions, but does not have the U.S. Ordnance Bomb on the ricasso). The Model 1913/17 will interchange with the Model 1917 but not with the P1907.
These were manufactured for the U.S. "Enfield" or "Eddystone" .303" caliber rifle (not to be confused with the British No.1 SMLE series which accepts the British P1907 Bayonet).
Bayonet examples made in the U.S. are stamped with model date "1917" over the manufacturer's stamp (in this case REMINGTON in a circle). Reverse is stamped with the U.S. Military "ordnance bomb" (aka "flaming onion") logo above "U.S."; to the left is an "eagle-head" over a date of manufacture (in this case 1929); to the right is an "X" presumed to be a testing or proof mark (perhaps a bending test as with the British counterpart).
Manufacturers were Remington and Winchester (the latter being quite scarce). Blade is made of steel, grips are of wood with two horizontal grooves cut into the sides; pommel will have an "oil-hole."

Scabbards were either green (olive-drab) fiberglass with steel throat or green leather body with steel throat, drag, and belt hook.

Please Note: These are currently being reproduced and offered by various distributors. Beware of these being offered as originals by secondary sources.