This item turned up at a retro fair. It was hiding under a table . The guy who was selling it didn’t know what it was .That was definitely to my advantage. I have given it a clean and service and it works fine. It would normally work on a 1 second pulse The key was missing but I managed to file down a similar key and get it to fit . I don’t now anything of its history . It should of had some labels on the back but sadly these are missing.Maybe someone knows more than me.Andy 