This Thompson Center (Williams) manufactured late variation red fiber optic adjustable rear sight assembly with both mounting screws is for the Thompson Center Omega in-line muzzle loading rifle when used with the taller .445" high fiber optic front sight and is in excellent condition with light wear.  (file photo)

Note: Thompson Center Omega muzzle loaders with the following serial numbers have been observed with this part:

Omega: VBZ4642

Omega X7:

Omega Z5: Z56443