I went to a program about identifying feedsacks and learned the only positive way was seeing the holes where they were sewn together. Many fabrics that were used for sacks were also sold by the yard. The fabric does feel coarser. Did the fabric you got from your aunt have those "stitch holes"? If so, save small pieces of them. I made an envelope & put some of those in it and attached it to the back of my quilt. My friend used that as a "frame" around her label.