Here is the Wikipedia link for the cover of “Will The Circle Be Unbroken” by the Nitty Gritty Dirt Band.
http://en.wikipedia.org/wiki/Image:The_Nitty_Gritty_Dirt_Band-Will_the_Circle_Be_Unbroken_%28album_cover%29.jpg

Here is the link for the Naval Historical Center page for Adm. David Dixon Porter
http://www.history.navy.mil/photos/pers-us/uspers-p/dd-portr.htm

It looks like the same person to me. I think they chose this picture because it would be hard to identify the service and time period, but we know, don’t we?

You might need to copy/paste the above links if they are truncated.