Chest plate

The chest plate was a component of certain Cyber-bodies. (PROSE: A Girl Called Doubt)

The Cybermen of Pete's World had the letter C engraved on their chest plates to represent the company that created them, Cybus Industries. Their emotional inhibitors were located beneath these plates and could be disabled by sufficient trauma such as an electromagnetic bomb. (TV: Rise of the Cybermen/The Age of Steel) Another group of Cybermen, organised into the Cyber Legions, who were all but identical to the Cybus Cybermen, were distinguished by their chest plates which lacked the letter. (TV: A Good Man Goes to War) Yet another was distinguished by the outline of a Cyber faceplate where the logo of a Cybus Cyberman would be. (GAME: Blood of the Cybermen)

"Cyber Legions" model Cybermen which appeared on the Mondasian colony ship had chest plates which could glow with a blue light, appearing like the chest units of the later weapons-grade Cybermen. (TV: The Doctor Falls)

Behind the scenes
Character Options released a Cybus Industries Cyberman action figure with a removable chest plate.