Purveyors of porcelain ceramics -- often called pottery or china -- first identified their pieces using hand drawn marks including initials or simplified objects, such as a bow and arrow or crossed swords. As demand and production increased, hand lettered marks were replaced by stamps. Many companies used a crown depiction within or as the actual mark. A reference list of crown marks on pottery is indispensable for identifying one from another.
Copy the mark you wish to identify. A scanner will give the best image quality, but you can also use a copy machine. In almost all instances, manufacturer's marks are placed on the underside or base portion of the object. If you can draw or use tracing paper, you can copy the mark by hand instead of using a scanner or copy machine. Either way, you will need an easily transportable facsimile of the mark you are researching.
Observe the mark using a hand-held magnifying glass, if needed. There are many marks containing crown figures and they can all seem to resemble one another if you don't look carefully. Not all marks are drawn or stamped; some are impressed into or, more rarely, embossed on the clay before firing. Having all the details before you during your research will help you obtain the results you desire.
Note the colour of the mark. This detail is significant when identifying any marks on pieces of pottery. Blue, green, red, brown and black were the most common stamp colours. Take note of whether the mark is beneath a clear glaze. The term "underglaze mark" refers to this trait, while "overglaze" means the mark has been applied after the piece was glazed. This is another time that a magnifying glass can be helpful.
Find some good reference books. The least costly place to locate research books is your local public library. Even small libraries have sections for books on collectibles and antiques, so start there. The Internet can be a good source for images of pottery marks. Second-hand bookstores often carry out-of-print reference books. Don't overlook periodicals about antiques and collectibles; these are usually written by experts and offer valuable information, as well as illustrations.
If you know the factory name associated with your china piece, you can be more specific in your search for its crown mark. Many of the more collectable pottery manufacturers have books written about the pieces they distributed.
Find the exact replica of your crown mark in the reference you are using. Factories often used more than one mark simultaneously, but they did not duplicate each other's marks. However, forgeries are known to be in existence for such pieces as Capo di Monte porcelain, whose mark is a crown over the letter N. Sadly, you can identify the origin of your mark, but cannot, in all cases, be assured the piece was made by that manufacturer.