If you ever wanted to check what version WMF in a quick way, here is my tip for you:
The installation package for PowerShell comes inside a WMF installer. Thus, the version of the WMF installer matches the version of PowerShell; so all what you need to do is to simpley query the PS version as seen below
(host).Version
in my case WMF version 5.1 is installed thats why I am getting the result shown as below

thats it! happy Powershelling : )