Ok I'm only taking a guess at this. The face of the watch has the look of something made in the late 20's early 30's just by virtue of the decorating on it. It just say's 1930 which could be what the number 30 is. The date of manufacture. The other number could be the run number, Z J, no idea.
This what I found. " Between the same years most Bulova watch cases also had a serial number that started with the number corresponding to the year of assembly." Ok that would make it a 1930 watch. Sorry that's as far as I could get. Good luck on a very cool find.