Abstract: A window structure for closing an opening in an upright wall of a cab structure composed of upper and lower glass panels having adjoining horizontal edges. A horizontal hinge connects the upper edge of the upper panel to the cab structure so that the upper panel can swing inwardly to an upper horizontal position just under the roof of the cab. The lower panel may be mounted in the lower portion of the opening or on the rear face of the upper panel and when in the latter position, upper and lower panels may be swung upwardly against the roof of the cab and latched in this position. A gas-pressurized cylinder is used between the cab structure and the upper panel to aid in both raising the panels and to restrain the panels as they are lowered.