Hello!

The tally sticks are simple tools: primitive men used them as sheets of paper.
Imagine you are a primitive woman and you want to count how many primitive dresses you have in your primitive wardrobe, but you have so many of them that you can't keep the count just with your mind, so you need to write it somewhere, thus you take a bone and sharp stone, every time you take out a primitive dress from your primitive wardrobe you put a mark (!) with your stone on your bone (!), until you get all the dresses out the wardrobe; by doing this you got a representation of the number of your dresses on a stick, if you count all the marks you can easily get the number of the dresses.
Now your marks are "tally marks" and your bone is a "tally stick".
I hope the idea is clear.

If you want to know more about the mega calendar/clock, aka Antikiperra Mechanism, you can read the Derek De Solla Price ideas in his book "Gears from the Greeks: The Antikythera Mechanism--A Calendar Computer from CA. 80 B.C."

Thanks for being here!