An Arrowhead
The object was, in fact, an arrowhead. Lukas could tell that it was very old. It must have been long buried and forgotten before the zoo even existed. He imagined how it must have belonged to a Viking from centuries ago.
The Viking would have probably looked a lot like Lukas since Norway is one of the original settlements for the ancient people. Lukas knew he had to show someone what Isak had found.