The Letov Š-1 reconnaissance aircraft first flew in 1920 and the Š-2 was a re-engined version. 28 and 64 examples were built, respectively, and c/n 44 was the 16th Š-2, hence the reported serial; I'm not sure of the correct format. The aircraft wears the insignia of Aviaton Regiment 1 which was based here at Kbely.
The Letov Š-39 light aircraft first flew in 1931. A batch of 23 machines, powered by 55-hp engines, was built for Czechoslovak aero clubs. The Š-139 and Š-239 had more powerful engines. This replica was built in 2009.
The beautiful Avia B-122 was quickly developed for an international aerobatic competition held in Paris in 1934, and it was quite succesful. 60 examples of this dedicated aerobatic aircraft were built, the improved Ba.122 version having a larger rudder and ailerons on both wings. 45 Bš-122 military trainers were also built for the Czechoslovak air force.