Ethiopian Orthodox relics? What ARE these ancient objects?

Ethiopian Orthodox iconography isn't exactly my forté, but I'd like to display two of these ancient tablets which have come into my possession. I hope that someone more erudite may be able to enlighten me.

Each measures about 10 x 11 cm, and about 5 mm thick at the thickest point. The one above may be an image of a Crusader or a missionary. Another bears an interesting script which reminds me of Egyptian hieroglyphics or perhaps Coptic script, while there are also representations of St George killing the Dragon, Angels, and possibly the 4 Evangelists. Each piece is not flat nor perfectly formed, but shows the irregularity of hand-carving, and is slightly convex - on both sides.

The material from which they are made? Quite heavy. Could be a stone like flint... but also sounds a lot like metal. What is the reason for the red colour persisting in the depressions? Ferrous oxides? Ink? Were these actually printing blocks for fabrics? And why are there three holes in each piece, as if they were originally bound like a book? Miraculously, a fragment of twisted leather (or gut?), slightly glossy, still lingers tantalisingly in one of the holes.

Mystery. See more photos and details here. luvian hieroglyphs cuneiform palmyrene alphabet sassanian texts proto-elamite texts greek alphabet cypriot script phoenician script cretan writing mycenaean linear b steatite archaeology religious artefacts religious icon religious icons holy pictures