"Part of a dummy's hand. Made of celluloid."
— Beginning Hour inventory description.
"Part of a dummy's hand. It's made of metal."
— Resident Evil 7 inventory description.
A not too dissimilar dummy finger can be obtained in the main game as well, by Clancy Jarvis and Ethan Winters.
In the main game, it serves as a mandatory key item for Clancy to progress through Lucas Baker's "activities" while it is passable by Ethan Winters should players know how to escape death by chronicling Clancy's exploits.
In the demo, the Dummy Finger can be found in a drawer near the blocked main entrance. In the main game, it can be found by burning the Straw Doll.