I dont know what a "curling ball" is. Are you meaning a "Hurley" ball? Hurley is a vicious and barbaric form of hockey which is still played in Ireland and the North East (Pictish Zone) of Scotland. Curling is played with polished forty pound granite stones on ice.

The beautiful bronze Walston Ball has, by some, been given a date of 200 AD. Others have attributed it to the Bronze Age. The later dates were originally given because the Walston Ball's "swirl" bears a resemblance to the pictish "swimming elephant" motif. Of course the 400 stone balls were originally given the name "Pictish Stone Balls" because many (but not all) were found in the Pictish Zone of North East Scotland and antiquaries deduced that they must be Pictish. Many of these balls have swirl patterns on them. It was in large part the in-situ discovery of the incredible Skara Brae balls and objects which eventually gave these items a Neolithic context.

The jury is still out on the Walston Ball.