I’d put it at more like 1940/1, going by the types listed.

Also, since the only Allied types are F.A.A. (Martlet, Skua, Fulmar, etc), then I think this has more to do with defence of the Fleet than the R.O.C.

Some form of ship borne device to range A.A. guns?

Edited to add that I hadn’t followed TT’s link but that is exactly what I had in mind – I used to have one of the American ones.