I have got round to photographing a few more things
Firstly a photo of all the different variants of keys for the Post Hatches.
Secondly, this is a very rare interface box. There would be several of these in the Group HQ's they would receive the call from Master Posts and there would be a headset attatched.
Seen here in York ROC HQ
Finally
All master posts were equipped with a Burndept 525 Radio. I am now lucky enough to own one.
Seen here in action: C/Obs Harry Wilkinson at Fleetwood Post, Lancs. Notice the speaker to the left. Unfortunatly i cant seem to find one - i will probably make my own.