Quality specification as in DIN IEC 60404-8-1
Example: NdFeB 200/220 w:
200 = Minimum allowed value for the max. energy density; here, 200 kJ/m3
220 = 1/10 of the minimum allowed value for the coercivity HcJ: here, 2200 kA/m
w    = code for the manufacturing process; here, die pressed