This dress appears to be from Sant Angelo's first 1969 Fall/Winter collection and is rumored to be inspired by Gustav Klimt's painting of Adele Bloch-Bauer. 

Multi-hued velvet, cotton, and metallic brocade maxi dress in gold/silver-tone braided trim patchwork, squared neckline, flared bell sleeves, and A-line skirt with center back zipper closure.  
Label: Sant Angelo

Approximate Measurements:
Shoulders: 15"
Chest: 41"
Waist: 36.5"
Hips: 60"
Length (underarm to hem): 43.5"
Sleeve (center back neck to hem): 31"