Now it is easier to find duplicates and unverified listings in Google Maps. You can do so via Google Map Maker.
This is documented by Linda Buquet in the Local Search Forums. In short, go to Google Map Maker and conduct your search.
Any results with the green shield is a verified listing, the others are not:
Google did not delete all unverified pages as some expected. Google only deleted or hide what they call "Shell Pages." Shell Pages are pages are any listing not created by a person AND not claimed will be deleted, according to Google. Pages created by humans will stay, Google told Linda.
This is the example Google gave:
Example: So if the page was originally created by Kelly ([email protected]) and she deletes it in her dash, it will stay in the local pack.If however, there was already a shell page on Maps for her business and she simply claimed that page when she verified, the page will be deleted (because its unowned and was created by 3rd party data).
So using Map Maker to find legacy or orphaned pages is still an important aspect of local SEO.
Forum discussion at Local Search Forums.
