He explained that most artefacts we find tend to come from either the era when Vikings were stereotypical marauders, or after they had begun to settle in Britain and Jorvik is flourishing.
This hoard, he said, is from "exactly the time when the great Scandinavian army invades to conquer Britain. The nation as a whole is going to benefit tenfold because this is going to enhance our knowledge of that particular period in Viking history."
The metal detectorists, who wish to remain anonymous, contacted Simon through the Portable Antiquities Scheme, a voluntary recording scheme for archaeological objects found by members of the public.
On show at Yorkshire Museum until the end of February, the finds will then go off to The British Museum for further study.
With a selection of silver items, the hoard is likely to qualify as treasure under the Treasure Act 1996. Once valued it will be offered to local museums and the fee split between the finders and the owner of the land on which it was found.
While Simon couldn't predict how much the hoard might be worth, "from an archaeological point of view they are priceless," he said. And as for how thrilled he was at the discovery, "more than words," was the verdict.