Australia 1950M Penny UNC
An attractive “woodie” or wood-grained pattern finish. Alloys have very different oxidizing behaviour. By 1950 Australian pre-decimal bronze is more or less 97.5/2/.5 Cu/Sn/Zn. Prior to that period it was many different alloys.
However, if the metals making the alloy are not heated and mixed correctly, then we have a multitude of potential alloy mixing errors. Some errors create laminate peel. Some leave gaping holes. A colourful, yet less dramatic alloy mixing error creates a wood-grained finish. The copper heavy alloy has oxidized to a duller shade of brown, while the alloys are still shining brightly.