Vintage MOD 60’s Shift Dress - Flower Power - Neon - Sleeveless - Size S?

Vintage, Retro, MOD, 60s Shift Dress - Flower Power - Neon - Sleeveless. Opens at the shoulders with fabric covered buttons. Princess seams down the front. Lined with silky white fabric. No fabric tag but it has a silky feel. Maybe nylon or polyester. Bright pink, green, yellow, and white. Brand - Arnelle Of California San Francisco No size tag so please compare the measurements to something similar you own. Approx measurements Pit to pit - 19 1/2” Length from shoulder - 36 1/2” Across hips 20 1/2” Maybe a Size Small? In good vintage condition. From a non smoking home. Bin /65 Would be great as a costume or prop in a play, movie, or TV show.