1970 the Royal Australian Mint released a Captain Cook Bicentenary commemorative 50 cent coin, these coins went into circulation, specimen cased, mint and proof sets. Below are some letters sent to the Editor of the Australian Coin Review magazine, and judging by the date, some keen collectors have spotted some differences very early.
30 plus years have passed since the release of these coins and the letters to Ed. It makes one wonder what other treasures have been revealed in the years gone by, and have we become lazy in not going through our personal libraries often enough.

ACR - June 70 - v6n12 p5........Letters to the Editor

COOK COMMEMORATIVE - 1970 Sir, - I am writing about the Captain Cook 50 cent pieces, as I have one which has not been struck properly.
On the reverse the date '1770' is not visible except for the '0'. Most of the word "fifty-cents" is not legible, and it has a black mark going across the back of the coin.
On the obverse the Queen's dress has not, got all the lines in it, and the lettering, especially the '1970' is not very clear. There is also no ridge around the edge of the coin. Yours, etc., MARGARET CANBIER Armadale, Vic.

ACR - June 70 - v6n12 p5.........Letters to the Editor

COOK SPECIMENS Sir, - Having examined six of the 50 cent Cook Commemoratives in plastic packs released on 13 April I found that each coin contained a blemish line.
I noted that this blemish line goes from the rim through 'ALIA 1970'. It varies from a slight shadow to, a heavier line but is not a Die Crack. From the few coins examined it could well be a sear line on the die used.
I consider the Cook Commemorative reverse to be the best seen on any Australian coin. May there be some thought to retain the Australian map for general 50 cent releases possibly with 'roo-emu' coat-of-arms placed within the outline of Australian map. Yours, etc., LEWIS W. OLIVER, Caboolture, Qld.

ACR - Dec 1970 - v7n6 p15........Letters to the Editor.

DECIMAL VARIETY Sir, - As a result of examining my four specimens of the 1970 50 cents, I believe I have discovered the first significant variety in our decimal coinage. Three of my specimens (one plastic cased, two from circulation) have the 'normal' date, the top of the '7' making an angle with the edge above it. The remaining specimen, from a mint uncirculated set, has a '7' slanted more to the right, its top being parallel to the edge above it.
I don't know yet which is the commoner variety, or whether these have already been discovered. - Yours, etc., W.J.CAMPBELL Canberra, ACT

ACR - April 71 - v7n10 p22.......Letters to the Editor

VARIETY CORNER Sir, - I have recently obtained a die variety in the 1970 50 cent coin. The 7 in the date, the top of which is slanted to the right and brings the top just above the '9'. The normal '7' is slanted to the left coming level with the '9'. This is a good die variety of which I have only found one..Yours, etc.,
A. READER Guildford, NSW

The image below shows two different positions of the 7 in the date. The top date has a "high 7" and tilted to the right.
The lower date has a "level 7" and appears upright with the other digits

An easy way to detect the difference, the crossbar of the "high 7" will be parallel with the edge of the coin, while the "level 7" will be seen to be at an angle to the edge of the coin

How common or scarce these types are I can not say, I was able to pick up one of each in Unc & Specimen (red plastic case) at a recent fair. Proof coins have had no mention in the early magazines that I'm aware of, I haven't checked any proof sets myself - your chance to discover a Proof variety if one exists.

Renniks 20th Edition - Mintage - 16,540,000 circulation; 554,000 specimen; 40,230 mint sets; 15,112 proof sets:
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