As Granitehill says, it is a CAT receiver made by Pye (who took over Rees Mace) as part of the 619/CAT emergency rig on naval vessels. There is also a Murphy version (618/CAS) which I believe was built to the same spec but is much "clunkier", akin to the B40.
I have the 619/CAT system operational, having obtained it from the HMS Collingwood museum in Gosport (sadly now threatened with closure). I declined the PSU on weight grounds and built my own, much lighter, version. Nice receiver, albeit a bit noisy. You can see details of my restoration at
http://www.tibblestone.com/oldradios...0and%20CAT.htm