I would be grateful if anyone could help me identify the "RA" makers mark on the case of this Brook & Son pocket watch. I am also confused by the date letter. I looks like it corresponds to London 1808 although Brook & Son were registered between 1891 until 1941 and were based at 87 George St, Edinburgh. There is a possibility that the watch was made to fit an older case but that doesn't seem plausible. It's more likely that I've got the date letter year wrong.
Thanks in advance.