Danny. Your #8936.
As far as I know there was no German (or British for that matter) requirement to write in uppercase; certainly my mother's letters to him were in her normal handwriting as were mine, at the age of seven onwards, though a good deal less legible (and far less legible if I did the same now).
A spot of light Googling tells me that Stalag Luft III was initially for officers only ( not aircrew only, or my father wouldn't have been there), but later an NCOs compound was added.
Re-reading my post (again) my mention of his portraits of fellow PoWs was confusing; the portraits were done in the camps, but must sureoy have been mounted later, as I can't imagine he'd have taken several of them A4 board-mounted on the so-called Long March.
There's a bit more to come yet, but I'll be abroad till mid-August.