Another house flag shown on the State Library of Tasmania website is that of Coal and Allied Shipping Co.:
“Medium yellow (...) house flag with a diagonal green stripe running from the bottom left corner to the top right corner. In the centre of the flag over the green stripe is a white oval with a black outline, and the letters 'C & A.' 'C' and 'A' are in white lettering with a black outline and '&' is in black. Coal and Allied were owners of the Stephen Brown.”
The photo is clickable, larger version here.
The Logo looks very much like the C&A clothing outlets logo but the colours are different and there is no wavy border around the oval.
Traces are found on the ’net of the ships Camira and Conara working for, if not owned by, Coal & Allied during the nineteen eighties, but I could not find any traces of vessels now directly operated by or for the company. Stephen Brown mentioned above is now a stationary training ship of the Australian Maritime College (see their site).
Coal & Allied presents itself (from their website):
“After 150 years in the Hunter Valley region of New South Wales, Coal & Allied is one of the major coal producers in the region, employing more than 2000 people across our three operations - Mount Thorley Warkworth, Hunter Valley Operations and Bengalla. Coal & Allied is also currently undertaking the Mount Pleasant Project and the Lower Hunter Lands Project. (...) Coal & Allied is managed by Rio Tinto Coal Australia.”
This firm was founded after the merger of Brown & Abermain Seaham with Caledonian Collieries in 1960. Additional info: CareerOne page on Coal and Allied [no longer accessible]