UK 9d Aerogramme Invalid After Decimalization - Taxed as Unpaid

 

UK 9d aerogramme (front only) sent to Australia in 1972 after pre-decimal stamps and postal stationery had been demonetized. 

Two-line instructional red handstamp „£.S.D Postage Stamps / Invalid from 1st March 1972“ and „By Air Mail“ routing instruction voided with a red six-bars handstamp. Diverted to surface mail.

Treated as a short-paid surface mail letter (3d Empire rate). Purple, boxed taxation handstamp, with a double deficiency of 6p added.

In Australia, a 6c postage due was calculated and paid by a 6c stamp at the Selby post office on October 23, 1972l

This postage due is strange as the tax fraction had to be multiplied with Australia’s UPU letter rate (10c) which should have resulted in a 6/5 x 10c = 12c deficiency. For an unknown reason, only the single deficiency, not the double deficiency was collected from the addressee.