I just picked up a chain to sharpen that I’ve never run across . It’s a Stihl .404 ,full skip chisel 81 dl . The witness marks on are about 30 degrees . But the cutter top plate angle is around 10 degrees . I can’t see where the chain appears to have been sharpened before . Any ideas of what type stihl chain this is ? I’ve run across ripping chain that is done at 10 degrees . But it was semi chisel . TIA for any light you can shed on this chain .