Hi Albrecht,
The .xll files do have an embeded version resource. However, in Windows Explorer the version information for the .xll file will not be shown by default. You can rename the .xll file to .dll and the check the properties to see the version information.
This will normally just be the pre-built Excel-DNA version information.
You can then have the version information from your .dll project copied to the .xll output by adding this project property to your .csproj file:
<PropertyGroup>
<ExcelAddInUseVersionAsOutputVersion>true<ExcelAddInUseVersionAsOutputVersion>
</PropertyGroup>
-Govert