Popular with variations. There are both clock-wise and counter clock-wise spirals and an outer loop enclosing them. The A. G. Newman version has  knurled bands on the side.  The Guerin version (1914), the Russell & Erwin ("Cantebury", 1897) version, H&D (1890 catalog) version and Bayer, Gardner & Himes "Winthrop", 1925 catalog pictures make it more difficult to see differences.  The Norwalk version used four ovals outside the spirals.