Counter

noun

1. One who counts

   "He's only 16 months, but is already a good counter – he can count to 100."

2. A reckoner; someone who collects data by counting; an enumerator.
3. An object (now especially a small disc) used in counting or keeping count, or as a marker in games, etc.

   "He rolled a six on the dice, so moved his counter forward six spaces."

4. A telltale; a contrivance attached to an engine, printing press, or other machine, for the purpose of counting the revolutions or the pulsations.
5. A variable, memory location, etc. whose contents are incremented to keep a count.