Our definition of antique Chinese porcelain follows to some extent customary practice here, where we live:
(1) An antique must show porcelain age signs.
(2) It must originate either in the early republic, Qing or Ming dynasties, or earlier.
The question is what is considered "early republic" period? We usually consider anything made after the Qing dynasty (1644-1911) during the 1910s or 20s as early republic, thus for us it ends 1930. Anything produced later is qualified as "vintage".