I have noticed phones with a handset (like the one in the image) have a little cover that resembles something like a cold camera shoe under the bottom of the handset’s top speaker holder. Is there a use for it? It has a line bump in the middle, but it doesn’t go all the way from both sides, it leaves a gap. I have also seem some of them have extra space on the top of the cover, and some don’t.
Not just a U.K. company, the GPO were the General Post Office and ran the entire phone network and more: https://en.m.wikipedia.org/wiki/General_Post_Office