with coins up to the year 1989 (I think) they hand punched the MM so it could vary in location your coin is within acceptable standards for the MM. The MM as of 1990 is included in the working die so it will always be in same location. Edited to include that some mis placed MM can be worth a premium but it has to be extreme.
@Nolan Workman If you'd like to see how wildly the placement of the mintmarks can be, just look at some of the Kennedy half dollars of the 1970's. Chris
