Based on the way the brim & curl is reacting to your thumb pressure I don't think it's necessarily a stiff Western weight felt. Also seems to me the brim would be more beat up if it was stiff Western weight. I'm also not sure that it is a 4X but I couldn't quite bring it out. Between looking at the sweat & this pic, maybe you can. Depending on it's care history, in the extreme heat of Australia I can see how a 1960's - 1970's sweat could deteriorate quickly. The stitching looks to be in good shape. We don't know if it was sold new in Australia or brought there. Based on how it may fit you what would you estimate the size to be? Measure inside width & length. If you want to sell it I might have an interest.