Expedient rear sight

Managed to snaffle one of these in a trade I swapped a NOS unissued No.1 MKIII mag for it and picked up 32 round box of 1944 MW MkVII ball ammo as well for a few dollars.

I gather the milled area would be where one would place a small spirit level to level the sight of course after one ensured the action and barrel were level.
Not sure on the eye relief and there is no windage adjustment only elevation which by the pic is pretty rudimentary.
Markings are Central MkI* & M.L.E
Anyway a few of you may have used them in your shooting days it was a stop gap if you fitted a H barrel to No.1 MKIII, as the original sight base would not fit the "H" barrel without being split and re silver soldered on.
Mine on my Lithgow 1916 MkIII "H" barrel has been done properly as the sight base rings have been removed and the base soldered back into position, which makes me believe it was done in service.
The barrel is dated '37 which apparently is when a swag of them were done.

That's a 1st for me.
Great find.