Aero A.300

The Aero A.300 was a Czechoslovak medium bomber aircraft that flew for the first time on 20th April 1938 and, in spite of what its numbering could suggest, it was an improved and refined version of the previous Aero A.304.
It was designed by Aero to replace the locally-built Bloch MB.200 that were already obsolete by 1937. The Aero A.304 transport/bomber was taken as the basis for this new bomber project.
It was a monoplane of conventional design with retractable wheeled undercarriage that was powered by two Bristol Mercury IX engines which delivered a power of 820hp each and drove a three bladed two-pitch de Havilland-Hamilton propeller.
It was armed with three defensive 7,92mm VZ.30 machine guns. One in the nose, other one under the fuselage and a third spinal one in a retractable turret. It had a payload of 1000kg (2200lb) of bombs that were carried internally and a crew of four, pilot co-pilot, navigator and radioman .
Only one prototype was built at Aero's installations in Prague and, after being tested, it proved to be the second fastest Czechoslovakian ever built, only surpassed by the Avia B.35 fighter. Despite being so promising, the Munich agreements and the subsequent Czechoslovak national crisis, paralized the development and manufacturation of the project.

Sources:
1. https://en.wikipedia.org/wiki/Aero_A.300
2. https://forum.valka.cz/topic/view/3758