Generalwar,
A good friend of mine is currently doing some minor restoration work on the exact twin to your Fraser, a twin even to the .303 British chambering. Its case is very nearly, but not quite identical to yours as well. Unfortunately, some "backyard mechanic", in an attempt to tighten the rear sight assembly, buggered it up. As well, somebody at one time fitted a tang sight to the rifle, which was later removed. Is there a possibility that you might post a couple of photos of the rear sight on yours, from two different aspects, and preferably with the scope removed? That would be "the answer to a maiden's prayers" in restoring the sight to its original configuration.

Best,
Ron Vella.