International Sign (Language)
Contrary to popular belief, sign language is not a universal language. Like spoken languages, sign languages around the world are different.
International Sign (Language), formerly known as "Gestuno", is an artificially devised sign language. Gestuno is to Deaf as Esperanto is to Hearing.
International Sign is composed of vocabulary signs from different sign languages that Deaf people agreed to use at international events and meetings.
The "unification" of sign languages was discussed at the World Congress of the WFD (World Federation of the Deaf) in Rome, Italy, in 1951 before the "Gestuno" was first termed. Gestuno is roughly an Italian word for "oneness of sign languages".
International Sign is practiced among Deaf officials, as well as some culturally Deaf individuals, participants, and athletes, to communicate with each other at ease (to some degree) at the international-level meetings, conventions, and games.
The International Sign has been developed by Deaf people at the international events, such as World Congress of the WFD and World Games for the Deaf. The signs were selectively loaned from different sign languages around the world.
For example, look at these three words for "government" in three different sign languages.
Most likely a native or fluent signer would choose the third one which is more iconic (or "onomatopoeic") with the 'crown' and its association with the Scandinavian governments.
First of all, sign language is not iconic per se; however, words are selected that might be most possibly understood. Sign languages around the world are completely abstract and incomprehensible to one another (foreign signers).
Regular world travelers and international organization officials are competent in International Sign to communicate with one another.
However, International Sign is not practiced in home lands. Like Esperanto, it's not as productive as their natural signed languages.