This is a vintage field microscope, likely a "Protami" model by Hensoldt Wetzlar or a similar model by C. Baker of London. 
It is an early 20th-century portable instrument in black enamel and brass. 
The square stage suggests it was designed for specific uses like mineralogy, possibly lacking a condenser for light from the base
H-17.5cm
W-8.5cm
D-8.5cm
Boxed dimensions.