Brotherhood of Steel holotag (Fallout 3)

Every member of the Brotherhood of Steel, just like soldiers of the US Army they are descended from, wears a set of two holotags around their neck. They contain essential personal and medical information about the wearer.

In Fallout 3, holotags recovered from fallen Brotherhood members can be turned in to Scribe Jameson at the Citadel in exchange for 100 caps and XP, but only BEFORE embarking on the Take It Back quest