1958: Plans for the AMP Building are unveiled.

The AMP Building at Circular Quay (1962) is regarded as the first major skyscraper built in Sydney. I found renderings that were published on Page 1 of The Sydney Morning Herald on October 21, 1958.

The notable difference in the renderings is that the plant room which we see atop of the tower today did not feature, though the article mentions that the final height to the top of the lift shaft at 370 feet (main building was projected to be 347 feet tall).  It was envisioned that the new building would cater for the growth of the company up to the year 2000. Projected cost was five million pounds ($10 million).

Keep in mind that a decade later, plans were already underway for a second tower which would become the AMP Centre, which was completed in 1976.

The AMP Building is notable for the precdent that it set for highrise development in Sydney and Australia:

• First international style skyscraper in Sydney.
• At 117 metres tall, it was twice as tall as any skyscraper in Sydney. 
• Led to taller and higher buildings in Sydney. The AMP Building now is now a dwarf on the city skyline.

Source: Anon. "Untitled" (Artists Impression). The Sydney Morning Herald, October 21: 1. 

As part of AMP's Quay Precinct development, the AMP Building will undergo renewal works which will include the return of some of the lost features of the tower. The major renewal works will occur in its interiors with a major upgrade of office space to provide premium space for tenants. This is projected to commence in 2020. Changes will respect its heritage status.

It should hopefully be completed by its 60th birthday in 2022.