Incorrect postmark?

Dear Editor,

Lennox J Hernandez’s educational response was indeed well received. (‘No stamps conundrum,’ SN, April 16). I must share a new finding, and that is after I used a magnifying glass, I observed that the postmark on the Australian stamps reads ‘15 December 1955’ and the postmark on the British Guiana stamps reads ‘23 June 1955’.

It is impossible for mail to be posted in December of any year and received before that.  I think that the BG Post Office in 1955 stamped the incorrect postmark.

Yours faithfully,
T Pemberton