When Phil and Rosalie are talking on the roof of their building, there is a billboard for Frankel. Max Frankel is the Art Director for for the film.
The sign says Frankel and Black. Ralph E. Black was the Production Manager.
Phil drives a 1954 Lincoln Capri four-door sedan to Brooklyn to see his folks.
One of the mug shots shown to the witnesses has the name "Maxwell Shane", the name of the film's director.
The scene when Regal first goes inside a building to visit his mother was filmed on Second Street in Los Angeles, California in what is called Little Tokyo.
Lee Van Cleef has an uncredited role as the jewel fence Harry Goldish playing in the fixed poker game with Nicky Bradna. Van Cleef had begun his feature film career in 1952. He went on to bigger roles in westerns High Noon (1952) and For a Few Dollars More (1965). He died in 1989 at age 64 of a heart attack.