When Park Chang-yi throws the knife and impales the centipede, he is wearing modern boxer brief underwear.
When Park Chang-yi spins a supposedly 78-rpm record in Kim Pan-joo's office, the record he play is a 33 1/3 rpm Angel record. Angel records were not around in the 1940's (the record label is from the 1970's). Furthermore, Angel records specialize in classical music and would not release a record of Glenn Miller music even if they had been around at the time of this movie.
The railway sleepers are made of concrete. At the time sleepers was made of wood.
One of Park Chang-yi's gang uses an incorrectly identified British Sten gun. It's actually a SIG Bergmann 1920 which was imported by the Japanese.
Several members of the cast wear startlingly modern boots.