I've inherited all my grandfathers radio and telegraph equipment. I have lots of memories of sitting on his lap in his radio room while he talked to people on the other side of the world before the internet was really a thing. He passed away in the mid 90's and I think he would have loved this modern world and all its tools for instant communication.
This piece is likely from Signal Electrics Telegraph learners kit, there appears to be many eras of this kit from the 1920s until the 40s. I suspect he got this around the 30's but I'm not sure. Its a really cool piece of retro tech tho.
It is yeah. His other key has his call sign on it.