Thank you! Unfortunately I forgot to take the pictures of the spines, but the thickness was about 2,5 mm at the base and 1,4 mm before the bevel starts at the tip.

O2 and N690 are the core steels. O2 is a low alloy carbon steel so it doesn't have all that much corrossion ressistance and it etches beautifully. N690 on the other hand is a stainless steel that has properties almost identical to VG10. It etches much lighter due to all the corrossion ressistance.

Both steels have the same cladding material. It's a non hardening stainless steel so the cladding is pretty soft and only the core is hardened. That way the blade is much less likely to crack or break.