Court card or court sized card was the name given to a size of picture postcard

Postcard

A postcard or post card is a rectangular piece of thick paper or thin cardboard intended for writing and mailing without an envelope....

, mainly used in the United Kingdom

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

, which were approximately 4.75 x 3.5 inches and predates the standard size of 5.5 x 3.5 inches.
Court cards were smaller and squarer in shape than later cards and were used from about 1894 to 1902.. In keeping with the regulations of the time, they had an undivided back for the address only and the message had to be written on the 'front' of the card. Many fine examples of these still exist and are sought after by postcard collectors

Deltiology

Deltiology is the study and collection of postcards. Professor Randall Rhoades of Ashland, Ohio, coined a word in 1945 that became the accepted description of the study of picture postcards. It took about 20 years for the name to appear in the dictionary the first time...

 and philatelists

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...

 alike. Although mainly used in the UK, many were printed by chromolithography

Chromolithography

Chromolithography is a method for making multi-color prints. This type of color printing stemmed from the process of lithography, and it includes all types of lithography that are printed in color. When chromolithography is used to reproduce photographs, the term photochrom is frequently used...

 in Germany

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

.