It is fitting that this first day cover marking the opening of the post office at the Tindal RAAF base , near Katherine, in the Northern Territory, included an earlier stamp featuring a marsupial -a kangaroo. Tindal has long been under siege by wallabies which breed like rabbits and interfere with the operation of aircraft. How the problem was overcome , if in fact it has , has never been fully explained . It might be another job for the US Marines and a B-52 bomber from Guam .