Exchange 2007 Versioning

In Exchange 2007 RTM, when you view the Version information in the Exchange Management Console or examine the value of the AdminDisplayVersion property for Exchange servers in the Exchange Management Shell, it shows the version as 685.24. When you view the Exchange version information in the Windows registry, it shows 685.25. If you use Microsoft Operations Manager, it will also show version 685.25, but if you view version information in Microsoft Office Outlook, it will say 685.24.
Also, you click Help About Exchange Server 2007, you'll see a different version number altogether: 685.018. This happens on all Exchange 2007 servers. This has been remedied in Exchange 2007 SP1. The RTM version of Exchange 2007 SP1 is build 08.01.0240.006, which is also represented as Version 8.1 (Build 240.6). This version information is consistently displayed in the Exchange Management Console, the Exchange Management Shell, and in the About Exchange Server 2007 Help dialog box.
Finally, if you use the Get-ExchangeServer cmdlet and examine the ExchangeVersion property, you'll notice yet another different version number: 0.1 (8.0.535.0). However, this one does not refer to the version of an installed product, but rather the minimum version of the product that can read the object. In this case any Exchange server that is version 8.0.535.0 or later will be able to read this object (because the last changes to this object's schema were made in build 8.0.535.0).
After you install an update rollup for Microsoft Exchange Server 2007, the version of Exchange Server is not updated to show that the update rollup is installed. This issue occurs because the version number that is displayed by the Exchange Management Console or by other administrative mechanisms is obtained from the Exchange Server Object in the Active Directory directory service.
To update the version number in Active Directory, the account that installs the update must have permission to change Active Directory. Typically, Exchange administrator accounts in large organizations do not have permission to update Active Directory.
Cited from:
http://technet.microsoft.com/en-us/library/bb232170.aspx
http://technet.microsoft.com/en-us/library/dd424923.aspx
You need to check the proper registry key for patches:
HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Installer\UserData\S-1-5-18\Products\461C2B4266EDEF444B864AD6D9E5B613\Patches
When using powershell to query the Name, Role, Exchange version, and patch level I see this:

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