The lock numbers are probably 1871,
This date coincides with Milner severing their connection with Hobbs who had made their locks since 1852 but were starting to compete with Milner in safe production.
These locks are the intermediate powder-proof locks by Aubin Nettlefold (integral spring) before Milner took over lock production themselves with their own design as most commonly encountered with the 5 to 7 profile keyway.
This is the first time I have seen a List 2 with factory fitted dual locking. Most unusual.