This State Library of Tasmania page shows the house flag of Australian Offshore Services (image is clickable):
Caption: “Medium white Australian Offshore Services flag with a light blue border. In the centre of the flag is a grey anchor.” Rather a silver? cross ending in an anchor’s flukes and sprouting four curves at the top.
Establised at Southbank, Victoria (south of central Melbourne) this company serves the offshore industry. My findings are scanty - there are offices at Darwin (active in towage, salvage, and wreck removal) and Perth (active in petroleum exploration).
It seems AOS, in existence since 1985 at least, were once owned by P&O, the current owner being Farstad of Norway. In any case the firm was instrumental in developing a safety code for offshore operations (see Acknowledgments and Introduction from the code).
Australian Offshore Services. A P&O company operating from around 1978 until the tenders etc were taken over by Farstad Shipping when they became managers and apparently by 2004 were also taken over by that company. Their flag was white with a blue border and a blue spouting anchor being shown by The Log of 5/1994.