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.

membershipNumber

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

Thing > Property > membershipNumber

A unique identifier for the membership.

Usage: Between 10 and 100 domains
Values expected to be one of these types
Text
Used on these types
ProgramMembership

Schema Version 3.3