Repeater Lens Pair, later deeper more Curved version fitted to most MKII NKC7/8RMK Remanufactured.
These hand made reproductions use material that is more brittle than the originals.
Care should be taken not to squeeze the sides, or overtighten the screw. Advise using a 3 mm / 1/8" pop rivet washer with the retaining screw.