In fact was 1988 the last year. After could be some hub doubling but this is show on hole coin not only on the MM. The 1989 RPM is rare to find because they reuse some previous Hubs which needed to has the MM punch.
the coin is well circulate which made more difficult to analyze. I will need close pic but less zoom to discern. The angles of the MM first and the second are different. On the year, the normal MM the high of the MM is bigger then the lower part of the P leg by rapport to the profile.