The Saracen 5 gearbox attaches to extension pieces via serrated connections, also known as crocodile teeth fixings.
This 22mm backset variant has a unique cranked forend design with the code 05058 on the shoot bolt extension sockets to distinguish it from its flat counterpart.
These gearboxes are available with a 9.5mm deadbolt. The 11.5mm and 13.5mm deadbolt variations are discontinued.
They are sometimes stamped "AUBI".