What Is Value Of Australian One Penny 1920

Krause is next to useless in covering Australian pre decimals. The dot positions are dot below lower scroll, dot above lower scroll, dot above upper scroll, double dot (below lower and above upper) and no dot. The dot below scroll comes in both curved and flat based letter reverses. All other reverses are flat based. To complicate it further there are 2 obverse master dies (Indian and English) with the English found with dot below (scarce) and dot above lower scroll (very rare). Many catalogues also list the no dot English, but I have never seen a true example (my collection of 1920 pennies is huge and I have attempted without success to obtain one) so it would be extremely rare.
the Indian obverse is from at least 3 derivative master dies (possibly 4)and the English obverses may be from 2 derivative master dies.
Values range between 3 dollars for average grade dot below CBL (curved based letters) to over 30,000 dollars for the best English obverse coins (Unc grade)and dot over top scroll coins.

Your comment about the Perth Mint producing 1920 pennies is just speculation, Perth Mint records do not indicate the production of pennies until December 1921, well after they received 4 1921 dated dies from the Melbourne mint. While they had 1920 dated dies from Sydney, it is unlikely that they would use them considering the availability of 1921 dies.