I found this in my dad's stuff. It powers on and all display segments are working.

Although I am familiar with RPN, I can only figure out how to do simple calculations.

If you can instruct me on how to further test the unit, please contact me.

I also have the logging printer - listed separately.  

Produced by AI - Experience the precision of the ESI Calculimeter 4100, a robust RPN calculator designed to meet your mathematical needs with ease. Equipped with a versatile multimeter function, this device is an essential tool for anyone requiring accurate calculations on the go. Whether you're tackling complex equations or managing finances, the 4100 model is engineered to deliver reliable results. The calculator operates on a common 9V battery, ensuring that you can power through your day's tasks without the hassle of constantly changing batteries. It also features a convenient printer for those situations where a hard copy of your calculations is necessary. With its powers-on functionality, you can trust in the ESI Calculimeter 4100 to perform consistently when you need it most.