The correct answer to this open question is the following.
The defender ring that is on display in the Long Barrack Museum is "William Barret Travis."
In the history of the state of Texas, the Battle of the Alamo represent an important moment in the confrontation of Texans and the Mexican Army. William Barret Travis (1809-1836) was an army officer in Texas that fought against the Mexican troops to defend the Alamo. He died during the battle.
The Long Barrack Museum is located in the Alamo, in San Antonio, Texas. There you can learn more about the Texas Revolution and the main characters that made possible the independence of Texas.