My WAG is that Nic wanted the blood of Christ for some ritual work. The grail would have the most "residue" on it most likely, but each of the other objects would famously have some on them too, with the exception of the plaque.
But we dont really know what that is yet either. (my assumption was that it was the plaque affixed to the crucifix in most depictions of it, which bears the letter INRI) Seems likely if it was affixed to the cross, there might be some blood on it just by nature of where it was.