Click image for larger version.  Name: Circular Ruler(model).jpg  Views: 342  Size: 555.8 KB  ID: 15508Click image for larger version.  Name: Circular Ruler(top).jpg  Views: 330  Size: 544.2 KB  ID: 15509
Actually this ruler has been designed for drawing circular winding diagrams, but it seems to be a multi user ruler.