OK, sorry for the delay.

It is, as Jase wrote, a drift calculator, and as Bex wrote, it is for camera sighting. Fitted to PR.3s and PR.7s (for a while) it was used to allow more accurate overlap images when flying ‘strip’ photo recce (I believe, still looking into this :confused: ).

And yes Bex, I believe 773 should have one as well.

Pics show the sight in ‘action’, and as now fitted to WF922 at MAM.

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