Swaziland: 1953 Aerogramme Franked at Air Mail Letter Rate

This is NGK #14 sent from Mbabane (29 AUG 53)  to Australia. Interestingly, the stamps on the back panel were cancelled at Mbabane, the capital of Swaziland, whereas the stamps on the front panel were all cancelled at Johannesburg (31 VIII 53). 

Franked at 2s 6d air mail letter rate, because the aerogramme most likely contained an enclosure.