I was watching a documentary about the Ulfberht swords from Scandinavia, and one thing caught my attention: it mentioned that these swords were made over a range of time and location that was broad enough that they couldn't have been made by the same craftsman. That "Ulfberht" name, even if it started as a craftsman's mark, became simply a name for a sword of that particular style, design and quality. Effectively, it became a brand.
That made me wonder: when was the first appearance of "brand names" for products? (For the purposes of this discussion, we can define a "brand name" as an abstract label associated with a particular product and/or production facility, but not with any particular person or simple descriptor. So, not a "Da Vinci painting" or "Italian marble," but something equivalent to a "Nike shoe," where designers can come and go but the name retains its continuity.)
Were there product lines, like swords or dresses or furniture, in Ancient Rome that were known by name, independent of their maker? In China, or Medieval Europe? When did a product first become detached from its maker in the minds of the consumers?
Damascus steel, I think, should qualify: it's a product which was recognized by name regardless of the actual manufacturer. It is now defunct in the sense that the technology has been lost.
Many other interesting products qualify, from wines (Burgundy and Champagne) to cheeses (Swiss and Dutch). These are active in the sense that one cannot sell a wine and call it "Burgundy" unless it satisfies certain strict conditions.
Other product names became generic (e.g., china).
On archaeology shows I have heard of tiles being marked with the maker's sign that can be used to find out where the tiles were made even now. So trademarks and brand signs if not names have a very old lineage.
Stone seals dating to 3,500 B.C. have been found in the Middle East. The seals were used to indicate who made certain items. The ancient Egyptians, Greeks, Romans, and Chinese all used various forms of stamps or markings to indicate who made certain things, such as pottery or bricks. Not only did the marks indicate quality, but they also let people know whom to blame if there was a problem with the product.
The modern share-capital corporation only arises in the 1600's, with the Dutch East India company I believe. Prior to then, by definition, everything is a proprietorship or a partnership.
Earlier adoption of any concept similar to a share-capital corporation I believe to be impossible, as the accounting and bookkeeping concepts had not yet been developed to support its paperwork.
Further, I believe that the definition of brand given by OP must be strengthened slightly in order to be meaningful; namely of being protected under law, and not just a manufacturing technique. Under this my belief is the Ulfberht would not qualify, though perhaps someone else can do the research to settle this point…
Therefore I believe the logo and brand of the Dutch East India Trading Company, established 1602, meets the criteria as the oldest brand not associated with an individual or partnership.
Clarification - I am not claiming that only a share-capital corporation can own a brand - only that only a share-capital corporation can exist for long enough to meet OP's designation of the type of brand that OP is inquiring about - one that lasted for a period significantly longer than a single lifetime, and perhaps for much longer.