This block has recently been re-designed to increase the size of the line capacity, even though the sheave diameter has remained the same.
Although not visible in the photos, the hex nut securing the axle is, itself, secured by a small set screw. To remove the sheaves, you must first loosen the set screw, then unscrew the nut on the axle. The size of the hex wrench needed for the set screw is 2 mm.
