dibstone

from The Century Dictionary.

• noun A little stone or bone used in the game of dibs.
• noun plural Same as dib, 2.

from the GNU version of the Collaborative International Dictionary of English.

• noun A pebble used in a child's game called dibstones.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun dated, 19th Century A pebble used in a child's game called dibstones.