In one of the sacks were these two pieces.
I cut off the two ridges and I run all four sides along the table saw blade to clean them and I got two pieces 45x35x250 mm. One of them has a slight crack, but it is in a position where I would probably cut it anyway so not a big deal. This is enough for 4-6 knives, more if used as scales for smaller knives.
What is puzzling are the darker and lighter parts. Those are not sapwood and heartwood, palms do not have those, and anyway, I know of no tree where the outer sapwood is darker than the inner heartwood as would be suggested by the curvature here. I do not know what caused that color contrast, maybe it was cut close to the outer layer of the trunk, maybe it is decay, I have no clue. Palm trees do not grow around here so I have no knowledge about their variability and specific properties and no way to obtain said knowledge (google does not help).
It is not an extremely expensive wood but two pieces like this would cost me somewhere in the vicinity of at least 40,-€ plus shipping, so it is nothing to sneeze at either. These were, alas, the last surprise in my firewood treasure trove, the remaining sacks were all pure jatoba. Still, I can’t complain.