Yes, I've nearly finished my 1902 to 1936 shilling collection, and with the exception of some of the Edwardian ones, including the notoriously rare 1905, I've got the lot in either EF, UNC or BU. It's taken me several years and a fair bit of money. During that time I've noticed some interesting details. As you say those issued between 1920 and the pre ME 1926, have a lack of hair detail, which to the relatively ignorant might be mistaken for undue wear, and a mismatch in quality between obverse and reverse. Although in my collection, the one issued in 1920 actually has decent hair detail, one of the two 1920 types you refer to above. Another detail I noticed was that the lion's nose on the reverse, was much more subject to very quick wear in the pre 1920 .925 silver examples. It was the first place to suffer wear, whereas on the 1920 to first type 1927, the lion's nose was much more hard wearing. Even VF examples show less wear than GEF pre 1920 ones. Somewhat oddly, I found the 1921 very difficult to get in UNC condition from anywhere, dealers, e bay etc, despite the relatively high mintage. Similarly the 1930, though the low mintage that year makes that one self evident. The ghosting was most obvious during the examples issued in WW1. Differences in value are apparent between weak and strong strikes.