User blog comment:Dssdassw/questions../@comment-30303790-20120304081927

It's most likely just random loot. Similiar to the lore issue with finding jet, a drug not created until after the apocalypse, in closed vaults on the other side of the country in Fallout 3.

So you just get a little more for your efforts, at least for the draugr. Animals could be given the rare coin for loot, but as Blood Reaper said animals like shiny objects, giving a realistic answer for the appearance.