Thanks, these photos are very helpful. This probably confirms that the crown on mine isn't original as clearly the crown should have the same PVD finish as the case and pushers. The crown on my watch seems to have a painted finish with either brass or a gold finish showing through, rather than a hint of steel where the PVD has worn on the edges. Additionally the crown on my watch has only 20 'knurls' which seems to be less than these, although, curiously the knurling on mine appears to be finer.
It would seem that the crown on my watch was replaced at some time with one that is a good match in size and profile but it was painted over a gold coloured finish.
Any help in finding a correct replacement for an otherwise fine watch would be much appreciated.