Hi, that is the Mono JK.
The Mono JK was a pukka F1 car built to the F1-née-voiturette 1.5-litre s/c rules. Entered for the 1949 Czechoslovakian GP at Brno it did not make the race due to a practice accident - it was ruled out of the race after colliding with a truck!
The car was constructed by Brno resident Julius Kubinsky, with Karel Vlasin the driver at the local Masaryk track. Beaten by the Cisitalia-Porsche 360 to the title of world's first rear-engined F1 car, the JK monoposto was powered by a Roots-supercharged 1.5-litre Lancia Aprilia engine, making it a very rare and typical Italo-Czech 'Eigenbau'. The car was a non-starter at its only GP entry, its cooling system damaged terminally by the accident. However, the car did race in some minor national hillclimbs and Libre races during the early fifties