Re: United States Lines question

He was a Master of one of their ships "American Miller" for a trip from England to NYC Nov 23, 1955 and looks like his earliest trip on ship was 1953. ( At least in Ancestry.com ships crew and passengers database). Companies will give Company issued "Awards" for long and faithful service, especially if retiring.
My thinking this is a "United States Lines" medal not to be confused with the "Distinguished Service Medal Issued for the President" given to Merchant Marines, unless you have the medal or at least a picture of it to compare ans make sure which one it is.
Link to picture of DSM medal for Merchant Marines, last one on right. http://www.homeofheroes.com/valor/02_awards/03_dsm.htmlhttp://www.homeofheroes.com/valor/02_awards/03_dsm.html

Google "S.S. American Miller" to find a little on it.
Have you seen this website:
http://www.usmm.org/http://www.usmm.org/
Also:
http://en.wikipedia.org/wiki/Captain_%28nautical%29http://en.wikipedia.org/wiki/Captain_%28nautical%29

You might try the U.S. Coast Guard to see if they have a archive of Licensed Captains or Masters.