The "Tin Boy" was originally developed by blacksmiths of the Republic of Sydney in early 1950s, its design evidently based in that of the SN-42 Armoured Vest, though with additional cloth straps for pouches, thicker steel plating, an epoxy-nylon rear cover and a mirrored plate covering the back. Many of them were exported for the Federal Army, which equipped its combat engineer units with these armoured vests and also found them rather useful for its mechanised troops which did not have to walk much. Following the Oceanykan Revolution, in a pattern that would repeat itself numerous times, the new Federal Government shafted Sydney by continuing to produce Tin Boy vests for the new Oceanykan People's Army, while foregoing licensing fees.
A Tin Boy armour vest weighs in at 8kg, more than double that of the SN-42. It is composed of two manganese steel plates tightly incrusted into a nylon fabric, though with the addition of an epoxy-nylon back cover to protect from spalling and better distribute an impact's energy. These nylon fabric covers are produced in camouflaged patterns, giving the soldier additional concealment, and several appliances such as magazine pouches may be sewn into it.