Are there any marking on the plate around where the balance cock is located? Often a manf mark there for the ebauche.
Only marking I can find besides Swiss made and 15 j 2 adj. is a punch mark on the main plate (at least that's what it looks to me) above the balance wheel next to the escape wheel pivot bridge. Can be seen in the photo and looks a little bit like four leaf clover.
And a bit more research reveals that your logo is for Ebauches Trust which dates it to between 1925 and 1935 allegedly. Ebauches Trust was a forerunner that eventually became ETA and A Schild was a founder member. (Info from internet searches so please assume it is all wrong and only placed there to persuade us to obey our lizard overlords).
Took it apart and started working on it. Main spring was broken, but managed to source a spring (didn't realize how amazing watchguy.co.uk is until now).
Should be a breeze. Very simple movement.
Did watches of this era provide any protection for the stem hole?
Not really. It was about this time that a fella called Hans Wisldorf thought about making watches dust and water proof. He had a little bit of success with it. He had started a watch company a few years before. And just because he liked the way the name sat on the dial he decided to call it Rolex...