Anpex Souvenirs 1970 And 1972

In Scott's, the 1970 Captain Cook Souvenir Sheet has a notation after it regarding a marginal overprint and saying that .... "is of private origin."






There is also an "Official Souvenir of the 1972 Exhibition" which is a sheet with stamp reproductions with printed "Cancellations.






Were both of these souvenirs produced in cooperation with the Australian Post Office and was the Captain Cook Sheet valid for postage?

Backroads
Both Cook sheets were valid for postage.
50,000 Mini sheets were privately overprinted by Hawthorn Press Pty Ltd for sale at face value during the exhibition.
The Aust Post Office stressed that the overprint was not official. Existing legal controls did not extend beyond the stamps themselves,and as the stamps had not been defaced they were valid for postage.

I don't have info on the 1972 sheet.

Thanks for that bit of info. I guess my search is on for a used example of the overprint now.