As for the postcard that possibly arrived around the same time as news of Kenny's death, Mr Matheson is not sure how his grandmother came to know the man behind the very frank musings.
Judging from his prose style, the family always assumed Stan Miller was an entertainer.
Mr Matheson said that as his father had also kept the card all his life, there could have been some family significance.
He might have been told the story when he was a boy, but he can't recall.
Mr Miller whimsically describes himself as someone who "on the firing line of industry, in the struggle of existence, not as a tourist, has crossed the deep blue sea".
He describes the vanity and "extravagance in wartime" of having his photo taken in a mirrored room and made into a postcard, "for the princely sum of 5p a head, 5 heads to the card".
He jokes about any "fat head" being worth a penny, then says when he saw his photo he was alarmed at how little fat he carried.
He raced off to the nearest weighing machine, he writes, "to assure myself that it is not necessary to put some kind of ballast in my boots to maintain my association with Mother Earth".
He ends his letter that begins "Dear Mrs Matheson" with "Kia ora ehoa, Stan Miller".
Someone else might know who this man was who wrote to his grandmother, Mr Matheson said.
Regardless, he will continue to treasure the fascinating, if mysterious, family memorabilia.