At age 24 Mr Mackay had to forego playing rugby due to a recurring shoulder problem - he had just made the Taranaki team - and was asked by the-then fire chief Roy Glentworth and Mr Commerer to join the brigade as they needed another person on their waterway fire brigade competition team.
Mr Mackay's commitment never wavered. A self-employed builder, in the 1980s he employed two fellow firefighters. "So when the siren went, the whole firm closed down.
"We are a strong brigade. Every member is prepared to do the training and put the time in to do the best they can. It is satisfying to be part of a great team of people. Everyone contributes in different ways, and such are the skills and talents in our brigade it is easy to tap into someone's expertise in a certain field."
The station was planned by Mr Mackay in 1970 with few changes by the architect.
In his 50 years Mr Mackay has attended over 4000 musters, meetings and fire calls. In the Eltham brigade's 110 years there have been nine chief fire officers and Mr Mackay has served under five.
He is the author of The First Hundred Years of the Eltham Volunteer Fire Brigade, published in 2002 for the brigade's centennial.
"They call me the brigade historian," he says, adding that he has kept scrapbooks since he was first secretary/treasurer 33 years ago - positions he still holds.
One of his proudest moments in the brigade was the part his sons, Kevin and Ken, played in the Eltham team winning the national United Fire Brigade competition in 2003, and when they were awarded life membership of the Eltham brigade. Kevin, who lives in Egmont Village, has since retired from firefighting. Ken is still serving in Eltham and last year received his 25-year medal.
Mr Mackay's hope is on one of his four grandsons, the eldest being 13, to follow in this family tradition.
"It [the fire brigade] is the best service organisation in the country anyone can belong to.
"It is a big ask, but it is worth it," he says proudly, honouring his wife Doreen whose support, he says, made it possible for him to receive the medal.