I wonder. On the currency pieces (1967), the wide rim came later - in 1968 - so I'd expect something similar on the 1970s. On the other hand, it may be that left-over currency wide rim dies were polished up for use in the 1970 sets, which didn't get produced until a few years after 1970. The London Mint was responsible for both, so who knows? I concur up to a point. If the narrow rim was an emergency use of an old obverse die, then these would be the last issued. The only one I've never had is the 3+K. If the above is true, then K should be the earlier die for 1970. Sounds reasonable, I'm guessing that an earlier 1960's narrow rim proof die was used inadvertantly (it appears identical to my 1960 proof) rather than the "correct" 1970 wide rim proof die or a polished 1968 (assuming it went wide in 1968) I've not seen any 1968 proofs so I don't know if they would have used narrow or wide.