Industrial design school chairs from the 50s

Set of four school chairs. Czech industrial style. The structure is made of gray painted metal. The seat and back are made of wood. One chair is smaller than the other three. Large chairs: Back height: 68.5 cm. Seat height: 38 cm. Seat dimensions: 35 x 35 cm. Small chair: Back height: 63 cm. Seat height; 34 cm. Seat dimensions: 35 x 30.5 cm. The whole thing is in its own right. Solid and stable. The welds are solid. The rivets on the back of one of the large chairs need to be tightened.