The Curta is a hand-held mechanical calculator designed by Curt Herzstark. It is known for its extremely compact design: a small cylinder that fits in the palm of the hand. It was affectionately known as the "pepper grinder" or "peppermill" due to its shape and means of operation; its superficial resemblance to a certain type of hand grenade also earned it the nickname "math grenade". Curtas were considered the best portable calculators available until they were displaced by electronic calculators in the 1970s.