Other mistake: Although the movie was set in the 1940s, one of the Japanese Army motorcycles was a modern dirt bike (long front forks, swing-arm rear suspension, etc.) modified to look old.
Factual error: Although the movie was set in the 1940s, the railroad track had modern concrete ties.
Man-gil: The bounty on your head is 300 won.
Yoon Tae-goo: What? I'm only worth a piano?
Man-gil: A used one at that.
Park Chang-yi: I'll play a game with you two. A way to get rid of both of you at once. A fun game. A game to decide who is best, where no one knows who will shoot whom. Where only one man survives. Right here, right now. I'll kill both of you.
Park Do-won: That'll never happen. I'll shoot you down first.
Park Chang-yi: We'll see about that.
Park Chang-yi: People must know that they're going to die, and yet they live as though they never will. Hilarious.