Abstract: A lower casing structure of a payphone is disclosed, including an outer casing member fit over the lower portion of the payphone and having threaded rods fixed thereon, a reinforcement plate having holes corresponding to and fit over the threaded rods, a coin container shield having a plate portion which has holes corresponding to and fit over the threaded rods and a flange having securing slots formed thereon and a support plate having holes corresponding to and fit over the threaded rods so as to sandwich the coin container shield and the reinforcement plate between the support plate and the outer casing member. Nuts engage the threaded rods for securing the support plate, as well as the coin container shield and the reinforcement plate, to the outer casing member. The support plate has a locking mechanism arranged thereon, comprising a rotatable member operable by a key to be rotatable between a locked position and an unlocked position.