Mid to late 1970s.
Australia started using centimetres (instead of inches) on labels in the early 1970s. Even then it's unusual as we mostly used inches until later in the decade.
Crimplene and Terylene are both types of polyester that were popular in the 1960s, and the style is of the 1960s too (with the boxy cut and hip tabs) but the measurement puts it into the following decade, I think.
As it's both a larger size, and an out of date style, it was probably a conservative shirt for an older man. The sort of thing my grandfather would have worn. The small collar suggests a later 1970s date, as collars were much larger in the earlier part of the decade.
Nicole