Signature of George VI, which features his regnal name (George), followed by the letters R for Rex (King) and I for Imperator (Emperor)
http://blogs.iwm.org.uk/research/files/2014/05/LO-image-low-res.jpeg

https://web.archive.org/web/20190803125328/http://blogs.iwm.org.uk/research/files/2014/05/LO-image-low-res.jpeg
George VI