A platen assembly for use with a money order printing machine or the like having a frame, means defining a printing line, type segments having printing characters positionable on the printing line and an operating lever. The platen assembly comprises a platen supported by rocker arms, and actuating mechanism means interconnecting the rocker arms with the operating lever. The actuating mechanism includes compression springs disposed between the rocker arms and the operating lever and control links adapted to selectively prevent rocking movement of the platen support arms. Initial movement of the operating lever toward a printing position creates potential energy through compression of the springs, which energy is released as the operating lever is moved substantially to its printing position and releases the control links thereby effecting impact movement of the platen into pressure contact with an instrument disposed between the platen and the printing line.