The literal translation of the title of this movie is: Blue Shield Safe. (The safe is where the diamonds stored). This movie is based on the true story that actually happened at the city of Nanjing (Nanking), the provincial capital of Jingsu Province, which was the Chinese capital from the time of the overthrown of the Manchu empire until the establishment of the People's Republic.
This movie is one of its kind in the Chinese movie industry in that it is the only film to date that describe the first generation law enforcement of post-revolution era. What is more important is that unlikely previous political propaganda made during the Cultural Revolution in which law enforcement are portrayed as genius and criminals are portrayed as dummies, this movie honestly describes the inexperience and inadequacy the first generation law enforcement of the People's Republic and consequently, the resulting near catastrophic failures, thus depicting the cops as the way they really were, just like any human beings.
The second importance of this movie is that it also honestly recognized the accomplishment and contributions of pre-revolutionary era cops who continued their services by joining the first generation law enforcement of the People's Republic after its establishment. After all, fighting crimes by capturing serial murders/robbers are all honorable contribution to the society regardless the political climate and political regimes.
The third thing that is unique is that this movie is the only one in which Mr. Shu Chen played a good guy. Mr. Chen also played a bad guy due to his look and this is his only known positive role. His name, however, is miss spelled as Xu Chen, instead of the Shu Chen, because he is so well known for playing the negative roles, and in this film, he played an misunderstood and suspected cop of the old regime who eventually turned out to be a good guy, and all of the suspicion and accusation against him were false.
The director of this film feared that Mr. Chen was perfect for the role, and indeed he was, but the director also feared that if the audience already had a negative image about the character Pang Chaoli played by Mr. Chen due to what he played in the past, the result might not be acceptable for the audience, since Mr. Chen was famous in playing bad guys. Remember, this movie was just made at the beginning of the reform in China, an era in the Chinese film industry still dominated by political propaganda, one characteristic of it is that good guys have good look while bad guys have evil look, and audience were accustomed to this formality. Since Mr. Chen's face could not be changed, his name was changed. Such measure proved to be completely unnecessary, however and this perhaps is the only flaw of the movie.