There are two types of QEII pre-decimal collector's pack with the £2 overprint, the regular pack with the overprint at the bottom right corner and the very rare overprint in central position.
Less than 50 were issued near the end of the pre-decimal era, the CTO date is September 24, 1965. It is not known how many of the 50 that were not sold were destroyed by the General Post Office but what is known is that some of the sold packs were pulled apart and the high values sold separately.
So to find a complete pack with the very rare overprint is incredibly difficult.
Front, back and inside cover
Australian stamps with the £2 overprint in central position
With additional stamps of the Australian Antarctic Territory (AAT), and the Cocos (Keeling) Islands.
One of the single £2 overprint stamps in central position without the collector's pack with some information I added comparing it to the the overprint in the lower right corner and the decimal $4 stamp