Casio SL-450LN

The SL-450 is a solar powered calculator that needs no batteries and still operates in low light. It has an eight digit, easy to read LCD display and it's rounded, hard, plastic keys are tamperproof. The four function signs are shown on the display at all times so you will always know what function you are performing. It has a square root and percent key and changes any positive value to a negative and any negative to a positive at the touch of a key.