On some Windows 10 machine with IIS 10 installed I have three Microsoft.Web.Administration.dll:
Two versions 7.0.0.0 and 7.9.0.0 in GAC (C:\Windows\assembly\GAC_MSIL\Microsoft.Web.Administration\) in 7.0.0.0__31bf3856ad364e35 and 7.9.0.0__31bf3856ad364e35 folders respectively and one version 7.0.0.0 in C:\Windows\System32\inetsrv\.
The following XML element in a Visual Studio project file adds a reference to version 7.0.0.0 of Microsoft.Web.Administration.dll:
<Reference Include="Microsoft.Web.Administration, Version=7.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35, processorArchitecture=MSIL"> <HintPath>%WINDIR%\System32\inetsrv\Microsoft.Web.Administration.dll</HintPath> <Private>True</Private> </Reference>
The same XML element with SpecificVersion=False will automatically reference the highest available version on this machine that is 7.9.0.0.