std::locale_id(3cxx) on Linux
The text 818d7a958ab0, as Debian 10 (Buster) shipped it.
Facet ID class. The ID class provides facets with an index used to identify them. Every facet class must define a public static member locale::id, or be derived from a facet that provides this member, otherwise the facet cannot be used in a locale. The locale::id ensures that each class type gets a unique identifier.