SKF is a Swedish bearing manufacturer that was founded in 1907.

Those hook spanners look old. They were made for tightening and loosening lock nuts that hold bearings in place on shafts in machinery, transportation and other industries. Judging from their size, I doubt that they were for use on bicycles.

Bearings mounted of shafts are usually pre-loaded to a specific torque value so that there isn't any play when in use under load.

Here's a modern version of SKF Hook Spanners:

SKF Hook spanners HN series

Chas.