PCGS - Collecting the coinage of Australia offers many varieties that are considered mainstays for any complete collection. This is especially true for the enigmatic dot varieties found on both 1919 and 1920 Australia Penny coins. For these two dates a total of 10 different varieties exist and completing a set of these coins is an incredibly hard task.
1919 (m) No dots
1919 .// (s) Dot above top scroll and below bottom scroll
1919 // (m) Dot below bottom scroll
1920 (s) Not dots
1920 .// (p) Dot above top scroll
1920 .// (s) Dot above top scroll and below bottom scroll (Image 6)
1920 // Indian Obv Dot above bottom scroll Indian Obv
1920 // English Obv Dot above bottom scroll English Obv
1920 // Indian Obv Dot below bottom scroll Indian Obv
1920 // English Obv Dot below bottom scroll English Obv
The dots were added to the working dies after hubbing so they are unlikely to be mintmarks. More likely they are test marks for die hardness. Check this DDR. No doubling of the dot therefore added after hubbing.
The title (Enigmatic Penny) is a rip off of what Fred chose as the title of our CAB article. And yes Echidna is spot on in pointing out that the "mint mark" was added post hubbing. If it was on the hub then the dots would be uniform is size and position. suffice to say that PCGSs cut and paste article is full of errors from their other source (the Benchmark Collection).