Hard Bernard's correct about the 50th/4 FTS connection
So why wasn't the aircraft painted "RAF Valley - 50 Years"? - a bit confusing, especially as 4 FTS was formed 89-years ago on 1 April 1921 at Abu Suier in Egypt to train pilots, primarily for squadrons based in the Middle East.
rogerk
4 FTS reformed at Heany in Southern Rhodesian on February 1947