Need help identifying two instruments ( compasses)

Hi guys I though this was the right place to ask for this type of help.

I have in my care two compasses each with an AM (Air Ministry) number on it and one has the type on it. Also one is slightly bigger than the other. What I really want to know is. What type of aircraft were these fitted to and if possible (a real long shot here) what aircraft (type) were these fitted to. I know it is a long shot as I know instruments were interchangeable from aircraft to aircraft but these might have a specific task.

Here is a description of the first. (the bigger one)

The face is six and a half inches in diameter.
The pin lines up north with cross hair lining up along the same axis.
The face can move via a small locking lever at the side so you can move the face round and take a reading after lining it up.
Air Ministry plate has a crown above it and if I am right the crown is the queens crown as it has a cross above it. (is that right??)

The AM plate reads

A M
Ref. No. 6A/1671

on the rear it has

ACO/R/44 stencilled and 1716/13 in ink

on the face it has Type P4A and No. 47060T

The second is smaller

the face with degree markings is missing but the rest is about four and a half inches in dianmeter the pin is reading north (as all good compasses do.
it has the same locking lever and I think the AM plate has a kings crown on it as it has a small ball in place of the cross.

the AM Plate reads

A M
Ref No. 6A/726

and has 1716/14 in ink on the bottom.

After looking at the ink numbers I think these must have been in an auction as the numbers are only a number apart and look like a lot number and an item number or they are stock taking numbers.

I also heard a suggestion that these may have been from a air sea rescue launch that may have been operated by the RAF.

Any ideas. Also if any one has any idea on worth.

Regards Merlin