Vintage Boho Lightweight Sweater

Beautiful arm band detailing on this vintage sweater. Purchased from a vintage shop a few years back, it’s a beautiful sweater that spends too much time in my closet instead of seeing the world. Labeled size 12, I think it better fits a 10, or a size M. Could also fit a S, depending on desired fit. Pre owned with no apparent flaws. No material listed but feels like polyester.