Of that win, a highlight because of who was there rather than that he won, he said: "It wasn't really his type of sheep, but I wasn't worried."
Coster has had more than 70 Open final wins, mostly in Canterbury and most prolifically at Mayfield, with 11 wins including five in a row up to last month's final when he was runner-up to up-and-coming Pleasant Pt shearer Ant Frew.
He thinks his first competition was at Methven or Mayfield, in the late 1980s, but his first Open win is thought to have been a Mid-Canterbury Circuit final at Ashburton in 1993. It was one of 85 competitions throughout the country that season, which compares with the modern calendar of just over 60.
His specialty became multi-breeds events, regularly the Canterbury All-Breeds title but with the greatest successes coming in the North Island where he had five PGG Wrightson National Circuit final wins over five different sheep types at the Golden Shears in Masterton and two in the New Zealand Shears Circuit final in Te Kuiti. Both events include merinos.
The only South Island shearers with more individual wins at the Golden Shears are thought to have been the great Snow Quinn (six Open titles, one Senior and one World title) and Colin King (three Open titles and six in the Circuit).
The successes in Masterton, including a string of placings, launched him into 12 transtasman tests against Australia and two Shearing Sports New Zealand team tours of the UK, and he was acclaimed a Master Shearer in 2014.
Among the more memorable was the first test trip to Warrnambool in Australia in 2007 with Paul Avery, and with Joe Paewai.
"We got our arses kicked, but we still had a good time," he said.
Sadly, Paewai passed away before they could reunite for the home test in Masterton a few months later. Another was the 2010-2011 series, with fellow Rakaia shearer Grant Smith, also a Master Shearer.
Coster, who runs a courier business with wife Sheryl, says he still shears about 25,000 sheep a year, and while Monday signals the end of the serious part of the competition career he expects he will still shear occasionally at "local" shows, especially if there's a need to make up numbers and provide competition for younger shearers trying to reach their goals.
"I'm still enjoying it," he said. "But the body starts to wear down a bit, and you do have to do a bit extra if you are following the shows around."
There aren't any young Costers around to step into his moccasins. Twin daughters Samantha and Jamie helped out in the sheds when they were younger, but he reckons that while they may have enjoyed it, he did point out that it might be what they were doing for the rest of their lives if they didn't do well at school.
He said that if there was one regret it was that he hadn't taken the chance to work in the North Island when he was younger, to get-up the speed needed to be competitive in the major North Island championship finals, a factor highlighted in his only Golden Shears Open final in 2006, when winner Dion King shore the 20 sheep in 16min 56sec, Coster taking 19min 44sec.
Coster was particularly hopeful younger shearers would compete at the Mackenzie show, and learning from such shearers as Smith. "That's where they learn," he said.