Anything that was made before I was born feels like an antique to me.
But the term "antique" is supposed to be reserved for items over 100 years of age. In any event, that term is thrown around so loosely that it's kind of lost all meaning.
In the case of lenses, I'd say anything that's not an anastigmatic. So basically, your Meniscus, Petzvals, Rapid Rectilinear/Aplanats, etc. If it's not a true antique, it's at least an antique design and can give an antique look.