Greaves and Vambraces in the rank and file

[MARCVS PETRONIVS MAIVS]

I know of one Etruscan representation of vambraces, on the Francois tomb frescoes, depicting the execution of Trojan captives. A leader (presumably Achilles) wears a bronze cuirass, greaves, and iron vambraces. But again, its Etruscan and from the second half of the 4th century.

Interesting. I suppose it would not have been too great a leap to go from shin protection to forearm protection, both forms of armour use the same principles. For swordsmen it would probably make more sense, as for swings and such your arm extends quite far forward and sideways, making it vulnerable to a counter swing which without the vambrace and depending on the point of impact could pretty much cleave your arm/hand off.