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.