WW2 British Directors No.7

My friend offered me this for sale, but don’t ask me what it was originally meant for.
He told me that it is a WW2 dated British No.7 aiming circle.
So I don’t know for what canon or artillery piece it was used, but it is a nice optical instrument.
Afterwards I got some further information.
Officially these items were called “Directors No.7” and were meant to aligning the guns of an artillery unit to point in the same direction ( zero line ).
It comes in its original case.
Case looks like it is repainted.
In the case there is also a kind of mounting were the optics can be installed.
Everything on the aiming circle is working very smooth and the lenses are clear from dirt.
It is dated 1943 on the side, together with some other text that I can’t read.
Keep in mind that it is pretty heavy.

Markings: mentioned in text
Condition: light used