the glass is internal window upvc. The glass is covered by plastic around the edges which is pretty flat (sorry as you see I am no expert!)

Steve, November 2009

hi steve special tool required to remove plastic bead this can be removed with a very sharp chisel but knowledge of this type of repair is essential as damage is very easily done and not easy to repair best have double glazing firm replace the unit
regards bob

r.machnik, December 2009