Base64 CNContact identifier with CNSuggestedContactStore prefix

On our backend we detected imported contacts with strange identifiers, that looks like CNSuggestedContactStore://YnBsaXN0MDDUAQIDBAUGBwpYJHZlc...AAA. Inside of base64 encoded strictly service information like $archiver, CF$UID, internalEntityId, SGRecordId, $classname. I think that contact identifier always should be in uuid format isn't it? Do somebody know what this contacts are and how to obtain them for debug?