The first thing I noticed was the "S" on this coin. I went to doubleddie.com and compared my coin to a picture of a 1946 IMM. It certainly appears to be an IMM.Let me know what you guys think.
The MM shown on your coin is normal for that year. Check out this website on the different S styles for different years. http://www.lincolncentresource.com/San_Fransisco_Mintmark_Styles.html