Old style GU Ferco latch only, 2 roller locks which are easily identifiable by their 70mm centres.
Operation: Lift lever.
Latch reversal: Depending on date of manufacture either- Push the latch in to reveal a screw in side of case. Undo screw to remove the latch, reverse, reinsert and replace screw or Insert small flat bladed screwdriver in the small slot on side of case marked R/L. Push upwards to release latch, reverse and reinsert.