A statue with the power to fix your mistakes.
With many legends and myths attributed to it, the Shield of St. John was wielded by the Prophet and bears the curse of fame for bearing holy magic. However, the only benefit the Shield could bestow upon the wielder is psychological.
Magic, by its very nature, would greatly help not just the PCs, but the masses, too. Here are some magic items that the commoners's use.
A sword with a mission
A toilet that teleports your feces onto the PottyPortal's Poop Hill.
"I once went questin' for Alexander Sehtolc's five clothes. Each item has a magic power that the wearer can use, see. And when you get all seven, each power is amplified. 'Course, I never could find Alex's boots."
-Old Gerald, man in the pub.
What to export or import....
Fabric: wool, linnen, silk...
Wood: raw-material, furniture
Metals: iron, gold, silver, copper...
Wine, beer, mead, spirits...
Animals: horses, sheep, swine, cows...
Coloring-powder (for fabric, ink...)
Raw-material to make fabric: unprocessed wool, linnen, silk...
Glass: Windows, figurines, glasses, raw-material...
Tea (not sure about my spelling here, but I mean the hot drink Englishmen drink instead of coffee!)