Many items only have a Freebase or Google Knowledge Graph ID. This page property will have us find them. See also T114617: Track the number of identifier properties on an item in page_props.
Description
Description
Related Objects
Related Objects
Event Timeline
Comment Actions
If I'm not mistaken we already have the total number of statements on the Item in page props. Subtracting the number of external IDs should give you the number of non-external ID properties.
Example: https://www.wikidata.org/w/index.php?title=Q2&action=info
Comment Actions
This does not give an efficient way for querying. For example I want to query items without non-identifiers by number of identifiers.