Determining if a piece of Nippon porcelain is authentic requires closely examining the Nippon stamps and comparing them to authentic stamps on antique pieces, or more modern stamps on fake pieces. For example, if the stamp contains an upside down wreath with an hour glass in the center, the item is a fake, since authentic pieces never used an hour glass in the stamp. Another method of determining a fake requires examining the pattern on the item.
A stamp or mark with jagged lines drawn around a rising sun, as opposed to straight lines, also indicates the item is fake. Another common forged mark contains a maple leaf that is approximately 1/2 inch in length, as opposed to the 1/4 inch length in authentic pieces. This particular mark also contains an "H" in the word "Hand" that is different from the original. The Real or Repo website contains a list of fake and original backstamps.
However, comparing the backstamp to known authentic pieces is not always a foolproof method. Modern fake items marketed as Nippon may have a stamp with an "M" incorporated into a wreath that is an exact replica of the original. As of 2015, it is illegal to create porcelain pieces with this replica mark, although many pieces were imported into the United States prior to this law taking effect.
Other indications that an item is fake include an orchard pattern or antique rose pattern with a maple leaf backstamp, and a green mist or Texas Rose pattern with a rising sun. Certain items, such as oil lamps, wine coolers, wall pockets, oyster plates and black ethnic collectibles, were never originally produced by Nippon and are therefore fake.