There is a page named "Skull cube" on Portal Wiki. See also the other search results found.
Page title matches
File:Backpack CUBE N SKULL FLAGS.png (128 × 128 (7 KB)) - 14:39, 1 May 2011
File:Item CUBE N SKULL FLAGS.png (690 × 520 (261 KB)) - 22:09, 14 July 2013
Page text matches
File:Skull Cube.png Skull cube(350 × 358 (157 KB)) - 20:36, 24 March 2023
File:StillAlive skull cube.png In-game screenshot of the unused "skull cube" from ''Portal: Still Alive''.(519 × 523 (390 KB)) - 15:57, 2 September 2017
File:Metal box skin002.png The texture for the unused "skull cube" found in the files of ''Portal: Still Alive''.(512 × 512 (170 KB)) - 22:44, 23 August 2017
