Well I don't know about the serrated bolts, but my 06A Norwood RSZ28 has dark phosphate bolts, they have "RBW' head markings, original, non serrated.
I recently restored a 02B Los Z28 and it had a mixture of "RBW" and "anchor" bolts also non serrated, very original car.
Both cars have wheel well trim. BTW.
Mike