Super mutant blood sample

The  is an item added to Fallout 3 in the Broken Steel DLC pack.

It can only be obtained after completing Who Dares Wins by speaking to Paladin Tristan. He will tell you that upon killing super mutants, their corpses will contain a Blood Sample. After giving ten to Paladin Tristan, this editor got 500 caps meaning they are most likely 50 caps each.