One of my friend was recently facing an issue while importing 2011 organization (database) into 2013 server using CRM Deployment Manager 'Import Organization' wizard. Unfortunately he was not aware of UR version installed on CRM 2011 server, as he had obtained only SQL backup file form the customer.
He received an error message "The organization database selected for import is a different version than the organization database that is currently deployed" during Import Organization Wizard 'System Checks'
Then while having a deeper look on the issue by analyzing deployment manager trace files (generally available in C:\users\%username%\AppData\Roaming\Microsoft\MSCRM\Logs\crm50dmsnapin), we identified that the database version is mentioned as '5.0.9690.3236' and it cannot be upgraded as it does not fall under the upgrade criteria.
You can only upgrade organizations that have Microsoft Dynamics CRM 2011 Update Rollup 6 (5.0.9690.1992) or at least CRM 2011 Update Rollup 14 (5.0.9690.3557). Upgrade rollups earlier than version 6 and Upgrade Rollups 7 through 13 aren't supported for upgrade.