Fullex SL16 has been around for many years, available in 35mm backset, the PZ size is 68mm and the spindle hole is split for Lever Pad option.
Fullex still manufacture these centre cases for use on new lock mechanism and also sell them separately for the repair market.
The latch can be turned to suit Left Hung or Right hung doors, this is done by remoing the one pozi retaining screws and removing the latch, simply place the latch back on the centre case the position you require and replace the Pozi retaining screws