4 Plia chairs by Giancarlo Piretti for Castelli vintage 1960

Suite of 4 old chairs in smoked perspex and chrome metal model plia design giancarlo piretti published by the italian firm anonima castelli circa 1960 in good condition. They are very clean although they display scratches and traces of use and some stings on chromes here and there. Everything is original. The chromes are clean, the seat and the back in perspex also. The special feature of this chair is its clever aluminum kneecap that connects the seat, back and feet, allowing the chair to occupy a very small space (only 5cm) when folded. The base is solid. Both are signed "plia patent anonima castelli.italy" inside the crossbar of the seat. A chair is 75cm high, 43cm for seating, 47cm wide and 50cm deep.