I hear ya, brass knuckles are pretty devastating, and where the blow landed based on the mugshot... Dude's zygomatic bones surviving without damage to the orbital, maxillary or temporal processes seem unlikely. Not impossible though.

Unrelated tip: A Bic type lighter held in your hand turns your fist into a concrete block without the impracticality of carrying a roll of quarters or a deadly weapon like brass knuckles. The absolute best option is to walk away.