Horses Hoof Fungus?

Description:

Paul Stamets owns a hat made of 'amadou' (the top layer of a conk): http://images.huffingtonpost.com/2011-11... . Amadou can also be used for drying fish flies. The whole fungus used to be used for carrying fire around since a small ember on the mushroom will last long enough to take fire to the next place. Photo 2 shows underside (pore surface). Photo 3 shows the layers of the conk. Photo 4 was taken 3 days later on the 6th Jan 2013 when the surface was drier. Photo 6 shows the reaction of the top layer (the top layer that has been scratched in photo 5) to KOH 25% solution. I think this was on silver birch but briefly looking at the pics makes me think again.

Notes:

sample cb(?) and a similar looking conk in the same wood was sample ca1