Chinese Porcelain Production Methods
 

Round Items:
Round items were thrown on the wheel. For a long time, at least from the Yuan dynasty to the Qing dynasty, items were thrown in two or more parts, which then were stuck together. Thus, jars, vases, bottles, etc. should always have one or more horizontal seams in the body of the item, which are clearly visible, often this was or could not be removed on the inside. In many cases the trace of a seam is also visible on the outside of the porcelain body.

Square or Rectangular Items:
(Early Chinese manufacturing methods before separable moulds appeared)

The flat sides of the item, be it a vase, box, etc. would be separately created by hand. They were then fit together.
Therefore, with older items you will often find that items are not perfectly square or rectangular. A good point to check with older items. Of course, very high quality items like imperial wares would still have been made carefully enough so that everything was perfect.


Protruding Ornaments (Appliqués):

Manual:
In some cases these were carved into the background material, but having a protruding ornament of limited size and shaving off all of the remaining background was often time-consuming. Thus, from very early on some of these ornaments were made by stucking the clay unto the flat surface. They may then have been worked on/carved further.

Moulds:
After moulds came into use ornaments would often have been moulded together with the flat sides. In some cases that was all finished this way, but with some the details of the ornaments would have been worked on further.

With hand-moulding, especially with figurines, but also with some rectangular or irregular shaped objects, finger imprints may be found on the inside. If there are none, we have to always consider the possibility that the item was made at a later time when machine moulding/injection was possible at the specific kiln or factory. Or, alternatively, the ornaments were stuck on later in old fashion as appliqué.

Just to give an example -- Dehua kiln which is known for its blanc-de-chine figurines and white wares, is known to have introduced moulds in the 1930s, relatively late. If you have a Dehua figurine that was moulded in two parts, then there is a good chance that it is later than that. We can use this for dating items.
Each kiln may have started using moulds at a different time.

This is not to say moulding started only in the 20th century. Some moulded ornaments were already made a thousand years ago, but not usually in closed or two-piece moulds.