Per Cole,
The Disston US 1943 was a standard US 18" survival machete from WWII. It originally had a rough black blade finish, and yes the handle is black plastic. Other makers producing this pattern including: True Temper, and Collins. It was used by the Army and Navy as part of the A-26 survival kit, and was also used by some Airborne Troops.
The Boyt Sheath is also period and if correct it will probably have a metal reinforced throat and collar and metal belt hooks.