Dallay is a French philatelic

Philately

Philately is the study of stamps and postal history and other related items. Philately involves more than just stamp collecting, which does not necessarily involve the study of stamps. It is possible to be a philatelist without owning any stamps...

 editor established in Paris

Paris

Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...

. Dallay has published stamp catalog

Stamp catalog

A stamp catalog is a catalog of postage stamp types with descriptions and prices.The stamp catalog is an essential tool of philately and stamp collecting...

s since 2001.

The catalogs list postage stamp

Postage stamp

A postage stamp is a small piece of paper that is purchased and displayed on an item of mail as evidence of payment of postage. Typically, stamps are made from special paper, with a national designation and denomination on the face, and a gum adhesive on the reverse side...

s issued by France

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 and other francophone areas: metropolitan France

Metropolitan France

Metropolitan France is the part of France located in Europe. It can also be described as mainland France or as the French mainland and the island of Corsica...

, French overseas territories, French post in Andorra

Andorra

Andorra , officially the Principality of Andorra , also called the Principality of the Valleys of Andorra, , is a small landlocked country in southwestern Europe, located in the eastern Pyrenees mountains and bordered by Spain and France. It is the sixth smallest nation in Europe having an area of...

 and Monaco

Monaco

Monaco , officially the Principality of Monaco , is a sovereign city state on the French Riviera. It is bordered on three sides by its neighbour, France, and its centre is about from Italy. Its area is with a population of 35,986 as of 2011 and is the most densely populated country in the...

. In late 2005, Dallay published a catalog for the French former colonial empire.

The catalogs provide detailed information about the stamps, such as, stamp designers' names, postal use at the time of issue, etc.

In 2004, Dallay was convicted by a court of justice of forgery

Forgery

Forgery is the process of making, adapting, or imitating objects, statistics, or documents with the intent to deceive. Copies, studio replicas, and reproductions are not considered forgeries, though they may later become forgeries through knowing and willful misrepresentations. Forging money or...

 and unfair competition for the use of Yvert numbering system which was first used in 1895. In March 2005, after arbitration by the French Conseil de la Concurrence (Competition Commission), Yvert et Tellier

Yvert et Tellier

Yvert et Tellier is a postage stamp dealer and a philatelic publishing company founded in 1895 in the northern French city of Amiens, where the head office is still located. The logo is a circle divided into a snowflake and a smiling sun...

began to license the right to print an index of Yvert stamp numbers at the back of competitors' catalogs. Dallay began using the index starting with the 2005-2006 edition.