Vintage Abercrombie Flannel Shirt-Jacket

This shirt-jacket is a thick cotton flannel with a red and dark grey plaid and vintage Abercrombie label. It was owned by my mad-men-era grandfather, a martini-mixing architect who took meticulous care of everything he owned. It has a structured fit and is in great condition. Label says medium but fits more like a small. My best guess is that it was purchased in the 80s.