This is a 1/8" thick brass sign found by one of my daughters at a yard sale. When radio installations were made on older ships in the 1920s and 30s, sometimes a new cabin was built to house them and it was called the Radio House.
There was one such ship in the 1959 Eastern Arctic Patrol Convoy that I took part in, she was the icebreaker "N.B. Maclean" (Call sign CGSN) and her radio house was at the stern. I was the 3rd Radio Officer on the Arctic resupply and hospital ship "C.D. Howe" (Call Sign CGSS.) Our radio room was on the bridge deck.