Worcester dinnerware traces its origins back to 1751, when it began producing porcelain in Worcester, England. What collectors know in modern times as Royal Worcester bone china dates from 1862, when the company became the Worcester Royal Porcelain Company. Thus the dating of Royal Worcester products begins in 1862. In 1976, the company merged with Spode, but still produced porcelain products. In 2009, the Worcester factory closed and the trademark name purchased by Portmeirion Potteries of Stoke on Trent. In addition to its famous bone china dinnerware, the company also produced earthenware and decorative objects like vases and figurines.
Look for the factory mark on bone china pieces. This is usually an underglaze stamp located in the centre of the base of the object. Royal Worcester uses a crown (noting its Royal Warrant given by George III in 1789) above a circle with stylised "W"s in the circle and "51" at the centre of the circle to denote 1751, the year of the founding of the company. You made need a magnifying glass to help read the factory mark.
Look for a number below the circle on the factory mark, and remember that the Royal Worcester brand of products actually begins in 1862. From 1862 to 1875 a two-digit number was sometimes printed below the circle denoting the year of manufacture. For example, a "68" would mean the piece was made in 1868.
Look for a letter code below the circle of the factory mark. This letter code is more common and used from 1867 to 1890. The letter "A" was used to mark a piece made in 1867, "B" in 1868, "C" in 1869, etc. The exception being that "O" was not used in 1879 as it would have been in the sequence, but instead "O" was used in 1889 (after "Z" in 1888). A small-cased "a" was used in 1890.
Use the Worcester Porcelain Museum's factory mark guide to find the date of manufacture for pieces made after 1890. The marking system gets more complex and a system of dots, asterisks and circles are used to denote the year of manufacture. Also, "Royal Worcester England" was printed around the outside edge of the factory mark circle from 1891 to 1927, "Royal Worcester Made in England" from 1928 to 1965, and several different lettering styles from the mid-1960s on.
Use the factory mark guide and other sources for dating Royal Worcester earthenware and porcelain products. It is often difficult to determine the actual date of manufacture for these products, but a rough date can be estimated.
Even though the factory marks are under glaze, they can sometimes be abraded or hard to read. You will have to try to interpret the missing or unreadable information based on the factory mark guide.