Stephen worked for Siemens and before that BBC Engineering. When he joined the BBC in 1971 quite a lot of kit still used the Mazda AC pentodes some of which had 'BBC Valve Department 1938' and the like marked on them. Such valves would have gone on for many more years had not the business requirements moved on. At least one attempt at replacing them with transistor equipment proved very much less reliable, but we still had the valve kit and went back to that.
Stephen has donated valves that had been in store for over 30 years. Many Thanks.