My old Hamilton field watch, being worn "upside down".
Recently I scratched the top of my wrist where it contacts my watch, and so as a result I've been wearing my watch face down, or upside down compared to the way most people normally wear it. To my surprise, while it seems strange to wear it that way, it's fairly comfortable.
Anyhow, a colleague of mind who normally wears his watch this way told me that he was trained to do that during World War Two, when he was in the Navy. The thought was that the luminescent faces of watches might be seen by U-boats scanning the seas at night, and if the watches were worn that way they'd be less likely to be facing outwards.
I wonder if that training was widespread, and if it was really based on a real danger? The faces of these watches aren't really all that bright, and I'd think the risk pretty small. Not that the Navy wouldn't seek to prevent the danger.