A heavy duty industrial electrical breaker or disconnect switch, also often called a fused safety switch. Used to cut power to large machines, shut down sections of factory equipment, provide emergency OFF control and isolate machinery for maintenance.
The large external lever mechanically opens/closes internal contacts — very typical of pre-modern industrial electrical systems.
Inside you can see heavy copper contact blocks, fuse holders or bus bars, multi-phase wiring (likely 3-phase industrial power) and mechanical linkage to lever. This would have powered something big like a press, mill, conveyor, compressor, or full workstation. 1940s-1960s.
Midlands Electrical Manufacturing (MEM).
