[RPZ28]

Sam, the only way to tell is to do a rockwell"C" hardness test on it, but the diamond tip from the tester will leave a small prick mark on the journal. The only problem with nitriding is that it is the hardest at the surface, the more you grind off the softer it gets. Yours at .020 under still should have some hardness left, at .030 under its usually complety gone. I hope this helps.
Ron