The round logarithmic ruler "KL - 1" is designed to perform mathematical operations of multiplication, division, squaring, taking square roots, finding trigonometric functions of sine, cosine, tangent, as well as inverse trigonometric functions, finding the area of ​​​​a circle. The set includes a passport with instructions and a box. Manufacturer: Moscow pilot plant of control devices “Kontrolpribor”. Moscow, 1964. WARNING! One ruler is fully functional. The second ruler does not work correctly: only one side rotates. There are traces of repair - the arrow is glued. This is shown in the photo. There is one original box and instructions in Russian. The box is damaged. It can be seen in the photo. Secure shipping with tracking.