It looks like an aluminium version of a sliding sash window, there are no glazing beads because it's what we call 'wrap around' so you'll have to remove the slider from the frame and remove the 4 screws in each corner and pull the frame off the glass and gasket, the gasket is a wrap around which surrounds the glass and the 4 aluminium sections thump over it clamping onto the glass, same as an aluminium sliding patio door, like this....