In The Orphanage by Serhiy Zhadan, Pasha was trying to go into a neighboring city to rescue his nephew from an orphanage. When he reached a train station, the attendants demanded to see his papers, from which they concluded that he was a teacher and was local to the region. (His papers evidently did not tell people which specific topic he taught, though, since the book elsewhere mentions that he was reluctant to tell people that he taught the Ukrainian language). However, when the book was describing his papers, the only paper it mentioned was a rather beat-up blue passport. I can see from Wikipedia that Ukraine issued blue internal passports until 2016. According to Wikipedia, it listed details like their registered address, date and place of birth, marital status, and details like that. However, I don't see anything that would indicate their occupation.
How did the attendants know that he was a teacher? Am I missing something about the internal passport, or was there some other paper that would indicate that? What was included in papers at that point?