my movie ticket anecdote: I have a box of movie tickets from over the years and just holding each one I can tell you about that day, what theater I went to, a lot of details that would be totally lost with a bunch of markdown files. I really think the physical card aspect is crucial

Plotting the find sites on a map shows that these petrospheres were often located in the vicinity of Neolithic recumbent stone circles.

They are usually round of reasonably uniform size at around 2.75 inches or 7 cm across. They can have from 3 to 160 protruding knob shapes on the surface. These carved stone balls are nearly all have been found in north-east Scotland, the majority in Aberdeenshire. As portable objects, they are straightforward to transport and have been found on Iona, Skye, Harris, Uist, Lewis, Arran, Hawick, Wigtownshire, and fifteen from Orkney. A similar distribution to that of Pictish symbols led to the early suggestion that carved stone balls are Pictish artifacts. However, examples have been found in Ireland and England.