Is it postal stationery?

Australia 2kg Prepaid Satchel - Ian McMahon

Is the "Express Courier International 2kg Prepaid Satchel" from Australia considered postal stationery?  Although inscribed 'prepaid' the satchel requires that the sender purchase a 'counter label' from the post office counter which is affixed to the satchel before it is actually 'preaid'.  The reason for this is that the rate for the satchel depends greatly on the country of destination.