The Lewis chess set that is used, the one that Imre Toth sweeps to the floor, does date to the 12th Century, but it wasn't discovered until the 1830's. 200 odd years after this film was set.
When the young boys in the forest discover the body of the girl, they run way and holler for help. In the next shot, the girl is breathing.
Just after Dobi buys the peasant girl "Young Bertha" and the shot pulls back to show people dancing,you can see three men in modern clothes along the bottom left. The one nearer the bottom center even turns a bit towards the camera, barely showing the black tie he is wearing with his white dress shirt.