Existence or non-existence of marks in a certain period is best determined through examination of large amounts of shards, found during excavation of kiln sites.
The heaps of shards found at any kiln site are usually the result of item damage developed during the firing process, or they are items that got stuck to the saggar, and needed to be discarded. It is estimated that generally only about 70% of all fired items were usable.
The shards can tell what decorations or marks were used during a certain period.
Before the Ming dynasty (1368-1644) none of the underglaze blue or decorated porcelain items manufactured at the kilns in Jingdezhen town had any marks, except with one example (see below).
During the Hongwu reign (the first reign of the Ming dynasty) there were no marks used.
Only during the Yongle reign (1403-1424), the reign of the third Ming emperor, white and blue porcelain made at the imperial kiln in Jingdezhen was marked for the first time. But only a handful of authentic reign marks are extant.
A Yongle reign mark would have the meaning of "Made in the Yongle years", the second Ming dynasty reign.
Today only 3 + 1/2 (three whole and one broken) cups are known (!) having this reign mark on their blue and white porcelain. They are in a museum, in Peking (Beijing, China).
Archaelogical excavations in Jingdezhen, in the strata of the Yongle reign, did not provide any further Yongle marks among the numerous shards unearthed.
However, also used in the Yongle reign were zodiac year marks, pictorial marks, auspicious marks, etc., but mainly by private kilns.
All these marks were usually written in underglaze blue on white porcelain. To be clear, however, only few of the items or shards marked this way were really from the Yongle period. Many porcelain items were found to have apocryphal marks, and were from later times.
The Ming dynasty reigns of Yongle, Xuande, Hongzhi and Wanli used marks written in
Zhuanshu style (a kind of seal writing), while the others were mostly using marks written in Kaishu
For Chinese speakers:
The Chinese marks of the Ming dynasty are often characterized as follows:
永樂款少, 宣德款多, 成化款厚, 弘治款秀, 正德款恭, 嘉靖款雜
Virtually no Chinese marks on blue and white porcelain from the Yuan
dynasty (1206-1367) are recognized as authentic, with the exception of one pair of vases now in the British Museum. These are marked as being from the "Yuan dynasty,
Zhizheng reign" and have been authenticated as
genuine. Everything else is currently considered as later made items with a spurious mark.
Even researchers in China seem to be convinced that NO genuine marked blue and white porcelain items from the Yuan dynasty do exist, apart from the above. Archaeological excavations in the Jingdezhen area did not bring any shards or other proof for the existence of such marks to light either.
Whatever the current status of the controversy with Yuan marks is, we can assume that no blue and white porcelain pieces bearing the Yuan dynasty mark "Zhizheng ...", currently circulating or being offered on the market, are authentic Yuan dynasty porcelain.
From the above it is fairly safe to further conclude that both, (1) the complete absence of authentic blue and white Yuan dynasty porcelain which is marked, and (2) the scarcity of marked porcelain from the Yongle reign (the reign during which marking began in the Ming dynasty), means that no marked porcelain having marks are authentic! If items with this kind of marks were on the market, shards with the marks would also have been found in the kiln shard mounds!
(So please don't waste your time and money thinking you happened on a rare exception!)
Any such item that appears on the market is therefore to be suspected as being a copy or fake made either later in the Ming dynasty or a modern fake. With many existing apocryphal Yongle reign marks it is actually known that such marks were used later in the Ming dynasty. This means they are not period items although they still are antiques.
Despite the fact that marking of porcelain really took off during the Yongle reign, the number of known authentic items from the Yongle period marked with a reign mark is actually very low.
It is therefore advised to always be wary of all items with a Yongle reign mark offered for sale anywhere. Such items are just too good to be true...