Rectangle coat by issey miyake (1980s), made from a lightweight, crunchy cotton-nylon with a slight sheen. The coat has an overlapped (slightly asymmetrical), 3 button front placket, angled welt pockets at the waist, notch lapels, and padded shoulders (unexpected for an otherwise soft coat, not unexpected for the 1980s). As might be implied by the phrase "rectangle coat" but will be spelt out explicitly by the following words: the coat is big and boxy.

Size M (womens/unisex), will fit S-XL depending on desired fit
Check measurements to confirm fit
All measurements taken flat

Shoulder width: 60 cm
Width (at underarms): 84 cm
Length (neck to hem): 115 cm
Sleeve length: 50.5 cm
Hem width: 90.5 cm

50% cotton 50% nylon
Made in japan
1980s