Black Leather Chairs with Chromed Metal Tubing, 1970s, Set of 8

Set of 8 beautiful chairs, in elegant black leather and chromed tubing,
very linear but still original design thanks to the delightful interplay of the armrests.
In good condition, they have some defects including some stains on the seats of some chairs, some scratches on the metal part, and a crack that has been glued onto one of the rubber tubes of the backrest (see last photos).
Two chairs have a label with an unrecognizable brand.

Width 50 cm
Depth 52 cm
Seat height 43 cm
Total height 75 cm
all other detailed measurements can be found in the photo.