Bill Heke scoffed with disbelief when an old army mate called last week to say his Vietnam War medals were for sale on Trade Me.

For the past 40 years, they had remained pinned to his old military uniform in his closet, and Heke had practically "never let them out of my care".

But despite his confidence, the 81-year-old Vietnam veteran immediately went to check his uniform at his Auckland home in Shelly Park.

On first appearances all nine medals were mounted in place as expected, but a small detail on the back of one medal left him "absolutely shocked".