I saw this in traffic last night, and was able to talk to the owner at a stop light, and ask him what the license plate means

It means he had the Mustang gifted to him on his 60th birthday! 

His wife gave it to him on his 60th... now THAT is a cool wife! It's a GTCS, and the guy looks like Carroll Shelby's brother. 

I told him he's a really lucky guy, and his wife is a keeper! Then I asked if she had a sister, and he laughed and told me that I DO NOT want any of that! HA!