A left handed dagger from 1575, well made in all steel construction. The term left handed does not mean it was for left handed people, it referred to a style of fighting popular in the late Middle Ages and is sometimes known as a parrying dagger. You would have a long sword in your dominate hand , normally the right, and the dagger in your left. This is where the left handed dagger name comes from. The dagger would be used to block your opponents sword giving an opening to strike with yours. Alternatively while parrying with your sword you could strike with the dagger.
The weapon gave you an advantage over an opponent armed just with a sword, you only had one weapon to watch, he had to watch two. The parrying dagger went out over favour by the early 17th century and was replaced mostly in Spain and Italy by the main-gauche, a much longer and heavier weapon. The museums weapon is a very functional device with a slender blade and protection for the hand.