Sold as Sheepswool by Schoolhouse Press, and as Fisherman by Black Oak Wool.
From the manufacturer’s website:
The reputation of Bartlettyarns has been built on Fisherman Yarns, our specialty since the early 1800’s. Carefully spun with select domestic fleece, Fisherman Yarns retain some of their natural lanolin for softness and weather resistance--ideal for sweaters, caps and mittens. Available in a wide range of colors, including four pure undyed colors: Natural, Light, Medium, and Dark Sheep’s Gray.
Note that the colors sold by Schoolhouse Press as Sheepswool are considered Fisherman 2-ply (or 3-ply) by Bartlettyarns.
Halcyon Yarn has a color card here.