[Joey][1] has [this trick][2] of embedding the Windows logo image within the kbd tags. So 

    <kbd>![Windows Key][winlogo]</kbd>

Combined with a regular key, looks like:

<kbd>![Windows Key][winlogo]</kbd><kbd>R</kbd>

Here's a better one that shows the 4 parts clearly:

<kbd>![Windows Key][newwinlogo]</kbd><kbd>R</kbd> `<kbd>![Windows Key][newwinlogo]</kbd>`

 [newwinlogo]: https://i.sstatic.net/B8Zit.png

Although FWIW I like the old one much better:

<kbd>![Windows Key][oldwinlogo]</kbd><kbd>R</kbd> `<kbd>![Windows Key][oldwinlogo]</kbd>`

Here are the images you have to use in your post's source code:

    [winlogo]: https://i.sstatic.net/Rfuw7.png
    [newwinlogo]: https://i.sstatic.net/B8Zit.png
    [oldwinlogo]: https://i.sstatic.net/T0oPO.png



  [1]: http://superuser.com/users/2054/joey
  [2]: http://superuser.com/questions/501239/how-to-open-explorer-with-mouse-only/501248#comment599076_501248
  [winlogo]: https://i.sstatic.net/Rfuw7.png
  [newwinlogo]: https://i.sstatic.net/B8Zit.png
  [oldwinlogo]: https://i.sstatic.net/T0oPO.png