Vintage Brutalist retailer sterling silver brooch, midcentury, geometric

This large brooch is in very good vintage condition. I have left it in as-is (tarnished) condition as I felt it suited the style and the patina added character. The pin and clasp are in good working order but there is some discolouration on the pin. The brooch is done in the Brutalist style in sterling silver, likely made in the 1960s. It is 1½" by 2" and comprised of values overlapping square and rectangular shapes. On the back of its marked "sterling", though quite faded, retailer and seems to have what is likely the artist's mark, but I can't make anything out of it.

This is a fabulous example of midcentury Brutalist jewelry design.