My wife carries a small Casio calculator in her purse.

Solar-powered, made of black and gold plastic and black vinyl, the calculator folds. When it’s folded, it’s about the size of a credit card and is as thick as two stacked cards. We bought it for a few hundred yen when we lived in Japan on Okinawa between 1981 and 1985.

We used it last night to balance the checkbook. As we finished, we talked to each other about how amazing it was that the little inexpensive still worked. Back then, the yen to dollar ratio was about 234 to 1.

Over forty years later, it’s a little worn but works perfectly. As I reflected on that, I wondered how many other things I’d ever owned that I could say the same about.