Avia B-534-II - Native Users

The Avia B-534-II was a Czechoslovak biplane single-seat fighter airplane from the 1930s.
The II series were a modification of the first series ordered by the Czechoslovak air force and comprised 45 airplanes.
Like the I series, they were armed with four guns, however, as the wing mounted gun in the original version was troublesome, these guns, upgraded to the vz.30, were placed in the fuselage together with the other two, firing through the propeller.

Some small number of them were tested with a bubble cannopy, certainly a very modern innovation for the era, but it was an experimental feature rather than an standard fit.
It was also powered by the Hispano-Suiza 12Ydrs V12 engine.

Sources:
1. https://en.wikipedia.org/wiki/Avia_B-534
2. Salamander Books - The Complete Book of Fighters