What rear sight?

[Flying10uk]

For a No.4 Mk1* rifle, what rear sights are correct?

Did you intend to say, what rear sights were originally fitted by the Long Branch and Savage factories to the No4 MK1* rifles which the 2 plants manufactured during the period of WW2? Was the micrometer adjustable rear sight originally fitted by the 2 factories to the No4 MK1* rifle during the WW2 period or would this sight have been retro fitted to this rifle (MK1* version)?