Abstract: A coding box suitable for a hot foil printing machine comprises a frame, a number of print wheels rotatable about a shaft with respect to the frame, each print wheel having a number of outward-facing peripheral flats bearing indicia, a through-hole parallel to the shaft and corresponding to each flat, a rod passable through the holes for setting the wheels in desired orientations with respect to the frame and a magnet in a cup for locking the rod in a set position. A second rod is provided, fast with respect to and parallel to the first rod and having an enlarged distal end for engagement with a hole in the frame to prevent complete removal of the first rod from the frame. The first and second rods are both fast in a handle by which they may be withdrawn from the wheels to permit rotation of the wheels, and thus variation of the indicia to be stamped.