core + attic (Attic Area): these terms have been either deprecated from the core or extentions, or removed from pending as not accepted into the full vocabulary.

schemaVersion

Canonical URL: http://schema.org/schemaVersion

Thing > Property > schemaVersion

Indicates (by URL or string) a particular version of a schema used in some CreativeWork. For example, a document could declare a schemaVersion using an URL such as http://schema.org/version/2.0/ if precise indication of schema version was required by some application.
Values expected to be one of these types
Text
URL
Used on these types
CreativeWork

Schema Version 3.3