My 2011 had the Ford logo, my 2014 has the horse.

 

I believe it has to do with certain packages or years. My 03 ranger had a raised blue ford emblem on the stock keys and airbag never saw another ranger with them and when i lost a key the only replacement Ford had was one that was an engraved logo they had never even seen one like i had. Im sure its a similar reason for the mustangs.

 

Here is how mine looks.

 

My 2011 had only 1 key when I bought it 6 months ago, and it had the Ford logo. I believe mine was a fairly early build.

As a condition of sale, I had them take the car to the Ford dealer and get me a 2nd key. The replacement key had the horse logo.