This is the "Master Mesh".
All heads sculpting and texture works always started from this.
In same time, this head is the final in-game mesh.
It means, all heads in this title share same topology, same UV.
It allowed to do morphing between any heads, then we could produced numbers of "mixed" faces.
Without it, we couldn't produce enough number of variation.
I estabblished the master mesh of male / female heads (they are same topology), and also master female body mesh.
After character artists' work, tech artist set pretty comprecated facial rig and skin weight data with automatic adjustment system.
It was actually surprising!