A knife from the Argus River region.
The Argus River was a flowing stream of water located on the planet Rigel IV. Carvings of the Hill People of the Argus River region were well known.
In 2267, the knife used by Redjac in a number of serial murders on Argelius II came from the hill people of this region. (TOS: "Wolf in the Fold")
This river was only mentioned in dialogue.