I have not seen the 853 top window in a while , but think it was held in with a rubber gasket if so -------One way is string , with the gasket wrapped around the window , put some 1/8 or slightly bigger nylon cord into the slot where the rubber gasket grips the metal and push the glass with the rubber gasket against the hole where it fits , as you push the glass pull the cord out which will flip the rubber into place , it helps to spray some soapy water mix or WD40 to help it slide , once the glass is in place you have to get the lock bead into place a window tool or a cotter ket removing tool will make that easier , put the hook under the lip and pull the tool along as you use you finger to set the lip , -----the newer machines use 4 bolts to hold the window down -----good luck what ever you do