I am now more convinced that the very worn Wreath pieces (and for that matter the 1935 Rocking Horse) have wear due at least in part to manual polishing. 0.5 silver coins were not minted from 1947 and I understand that the public were keen to hoard pre 1947 coins once they realised that new coins no longer contained silver. Hence those crown pieces probably only "circulated" till about 1947 at the most and I find it difficult for coins to get to Fine or less in such time scale.
However, I still believe that a small number did circulate (in the same way that the old style £2 pounds have circulated) for the reasons I already mentioned.