At work today one of the lads brought a 60mm Mortar to me to ask what the stamping around top of the barrel meant. The stamping read P.H.T 840kg/CM2 (as in Cm Sq) along with the serial number. At first guess I would hazard that it's something to do with barrel pressure etc but would appreciate any more informed/technical answers. I questioned a number of mortarmen but they didn't have a clue! Any of you technical chappies able to help out?