Grave good, maybe? Items that are sealed up from the elements can last a long time.

Item dating is often very contextual. Not only does writing help considerably, but a lot of context was lost in the chaos of the Spanish colonization/looting of South America, unfortunately.

That being said, sometimes, there just isn't enough context, even for Old World items, to get anything more than a very broad dating down. I've seen some pieces with ranges of thousands of years, lmao.