This is the calculator that my father bought for his senior year of high school in 1974. He showed it to me when I was four and I remember being amazed that a little box could add and subtract, captivated by the tiny red numbers. It was a few months later that he brought home our first computer, a Texas Instruments TI-99/4A, and I was again smitten. So much of the trajectory of my life can be traced back to those two objects.
When I opened the unit up I was not too terribly surprised to see a set of four AA batteries from the late 80's still installed, but I was very lucky that they hadn't leaked. I popped a new set in and it powered on with no issues. I played with it for a moment, the first time I had ever pushed the buttons on it, and placed it in the closet. I know it will be the perfect phylactery when I become a lich.
My dad had one of these. The 7-segment displays were pretty tiny, so he gave it to me when his eyesight started to degrade. I used to use it for my homework before I got my sweet Casio calculator watch. I remember the buttons feeling really nice.