The Omron 12SR, also known as "the Slide Rule", is the only RPN calculator build by Omron. The calculator has a nice green 14-digit vacuum fluorescent display. Besides the four basic functions this calculator offers a set of standard transcendental functions. The calculation speed is remarkable slow. Some calculations takes a few seconds before the result pops up.

The calculator can be supplied with three rechargeable AA size batteries. These batteries are charged inside the calculator by using an optional AC adaptor.

This calculator is not programmable.