Related Clues:
- Ancient calculator
- Pocket calculator predecessor
- Chinese calculator
- Tool that's counter-productive?
- Old counting-frame
- An old counting frame
- Counting-frame
- Early counting-frame
- Old counting frame
- Old counting frame with beads
- Instrument for rapid calculations
- An old counting frame with beads
- Ancient counting frame
- An ancient counting frame with beads
- Very early calculator