What object do the orcs start killing each other over in the tower of Cirith Ungol?

The Orcs in the tower of Cirith Ungol start killing each other over Frodo’s “shiny shirt,” the mithril vest. They discover the mail after Frodo is captured and mistake it for valuable treasure.

Frodo’s mithril shirt was given to him by Bilbo, who acquired it during his earlier adventures. It is a Dwarven coat of mail made from mithril, an exceptionally rare and light metal. Although it looks thin, it is strong enough to protect Frodo from a spear thrust in Moria.

In Cirith Ungol, the Orcs Shagrat and Gorbag argue over the shirt and the other items taken from Frodo. Their rivalry reflects the greed, suspicion, and brutality of Mordor’s servants. The conflict escalates into a violent struggle, allowing Sam to enter the tower and rescue Frodo.

The shirt is often confused with Sting, Frodo’s sword, or the One Ring because all three are important objects in the story. However, the immediate cause of the Orcs’ quarrel is the apparently ordinary-looking but immensely valuable mithril vest.