Renarts, you hit the nail. Dürer's drawing is dated 1493, so it is typical of an armoured rider of the late 15th century. It is said to depict an MAA (maybe even a poor nobleman, a 'free lancer' in the original meaning) as hired by the rich Nuremberg tradesmen to convoy their goods across the country.
There is an entire series of Dürer's drawings dated 1503 showing landsknechts of the very early type. None of them is mounted.