As found, where in the world?

Malta, Italy?

Certainly agree with all that, the differences between the myriad of 503 to 505s (Mk125-128) variants were the starters, s.chargers, fuel systems etc, but the 531 fitted to the handful (seven?) of late TPs was a different beast with the longer stroke and another 100 horses on tap.
I understand swapping it with the earlier type would be physically possibly, but wouldn”t it produce major paperwork and certification issues?
I do get that this only relevant if swapping from the late TPs, not the far more numerous early Mks.

Sorry my bad Bob, the early civil, and the military CC.1 Twinpin did share essentially the same lump as the Percivals, but the Srs 3 & CC.2 had the longer stroke 531 lump, I wouldn’t think they could be interchanged – but could be wrong!

BTW, I saw a picture of the ‘sky shouting’ Pembroke recently, but can’t remember where now!

I would agree with N66PK, which is ex Belgium Air Force C-51 RM-2 / OT-ZAB.
Pembrokes didn’t have bomb doors, so wondering if it has the camera hatches under the fuselage.
Guessing wires refers to trim or control surface cables.

A brand new Leonides is probably worth the opening price?

Photo recce, spotter/bomber, spyplane, transport, ambulance you name it, it could even carry passengers!
The APs allude to the fact that ASV radar could be fitted if needed.

Sea Prince T.1s have two bomb bays of course, similar to the B-29!

The Pembroke, in line with most RAF Transports of the time, had a secondary light bombing role, the description might be stretching it a bit but certainly not untrue!

Could it be from a fast boat?

Lovely post, and sorry to hear of your loss.