A region of spacetime from which gravity prevents anything, including light, from escaping. Standard feature of the super rare UG QuantumCompax. No idea.
It's for another stem tube for when the watch was ordered by a left handed person, thus the crown would be in a suitable position for LHW (Left Hand Winding).
Can you guys be a little serious. This is an old watch and this feature was very popular back in the day. It is a little pep hole that you look into to see pictures of naked ladies.
I saw that piece. The black dot is probably dirty polishing compound that worked its way into the hole. Note its presence in the other crevices of the watch. This was the strangest piece. Eustace, you want to post a pic of the caseback? It was bizarre looking.