I can't speak to coins, but I was discussing beads in Scotland with a PhD student last spring, and she says that she has found clear examples of beads imported from Sri Lanka at Roman sites in N. Britain. The problem is, few Scottish Roman archaeologists have been trained to recognize Sir Lankan beads (this researcher's skill set is unusually broad, because she worked on Asian sites for a year before starting her research in Scotland).

So we do have small, valuable objects from the east in the furthest western part of the Roman empire. Just, they're not coins.

Also bear in mind that one of the most important imports from the East to the Roman world was spices, which would leave no identifiable archaeological trace (unlike the coins that moved west -> east).

Not to be a bother here, but the article states two things. 1. The castle was active around the 14th century and 2. There was a 17th century coin also found at the site. Is it possible these coins are transplants? Brought over by other traders instead of global trade is the coinages' years?

Follow up: do we have a good explanation for how the Roman coins got there? Was it through trade?