During the 9th-11th centuries there was a series of late viking - early medieval swords all branded with ULFBERHT inscribed on the blade. The inscription most likely started out as a personal signature due to it being a common name but the swords where produced over a longer time span then any smith would live.

Lots of swords still exist today, about 150 of them have been found and includes a fair number of blades with the "brand" misspelled or the quality being below par which some suspect being pirated by forgery forges.

Although it's not quite the same thing as modern "Branding," advantages specific to certain regions led to their goods and services being labeled as superior or more desirable as early as the middle ages.

u/WARitter discusses 15th century Milanese armor-makers and their well-known "brand" in this post while I discuss the prestige of the 11th century medical school in Salerno here.