I may be wrong here but will soon find out as I have ordered a pound. I have worked from FWI blanks before. Many of the the blanks I have worked I assume were inner core blanks. They had a more crystalline appearance.
These seem to be no harder than the blanks that don't but they had much fewer faults in them after shaping at least 10 nut and saddles over the years from FWI I find it no harder to work than Cow bone. in fact I think my files like it better. Also the ones that are crystalline in appearance I have done don't seem as prone to chipping as the the blanks that look more elephant ivory like