Australia was big on assembling CKD cars with lots of domestic content. This is an aftermarket fiberglass hardtop with vinyl cover that was manufactured in Australia. Notice the sharp corner on bottom edge outboard at back. This appears to run all the way out to position of the piping at body to wing joint rather than curving around on top of the body tonneau as is more common. So far the manufacturer's name is unknown. Due to normally warm and dry climate, MGA hardtops are fairly rare in Australia (as are MGA heaters).