Wow, an abacus! I had no idea people still use those. My mom was an accountant, and she could work the contraption very efficiently. She could even do multiplications and divisions on it. I don't know how to use abacus, but we learn a slide rule in high school. We were not permitted to bring calculators to the math classes.
But you know what is the most surprising? My search for "abacus" on ebay resulted in 11000 hits!