In an effort to reacquaint myself with the differences between SD and LD on the four (4) known years where such varieties occurred, the following comparative collages have been produced.
As noted in multiple sources (including this site, LCR) some common points of differentiation are:
1960 SD, the 9 is almost the same height as the 1 and 0; and the inner loops of the 9 & 6 have different heights.
1970s SD: the 7 is almost the same height as the 9 & 0, the inner loop of the 9 points at the middle of the 7 (LD points at the base of the 7); LIBERTY lacks detail and is mushy in appearance. (Proofs have the same diagnostics)
1974 SD the 9 & 7 are thinner; the 4 is narrow with the triangle inside also being narrower; the lapel catches the light and appears raised on the LD; the bow tie is different; the motto and date are closer to the rim on the LD; and the details in the hair and portrait are mushier than SD but crisper and showing more detail on the LD.
1982 SD is naked eye obvious, date and motto are a clear crisp font; the 2 is different: the SD has a curved stem from the bottom whereas the LD is straighter.