Knuckle stat with normal Bear Knuckles and nothing else.
Calculation:
First we need to calculate the damage from the stats gain, that's easy... is 415/3.
*Remember to always subtract 10 from the stat because they are not accounted (with exception to magic attack).
Then we have to add skill damage bonus from Combat Mastery (18 max dmg) and Knuckle Mastery (20 max dmg).
Finally, we add the weapon damage (23 max dmg).
So overall:
415/3 = 138.3
20 + 18 + 23 = 61
138.3 + 61 = 199.3 -> 199
and that matched the damage shown in the window, so I don't see a problem with the skill bonus... at least not now.