The South African winger made his way into the club’s history books with 122 tries in 191 appearances when he played for the club between 1963 and 1968.
Former Trinity star Neil Fox, who played alongside, Mr Coetzer, told the Express: “His try-scoring record gives you everything you need to know about him as a player.
“He wasn’t a big lad but he was strong and tough. He was as good in defence as attack, a lot of wingers weren’t but Gert was good at both.
“He was a first class bloke, a gentleman, and we were sorry to let him go at the time.
“He would have done well in today’s game.” His try-scoring record leaves only Mr Fox, Fred Smith, Ernest Bennett and Dennis Boocker ahead of him in Trinity’s history.
Historian Lee Robinson, a former physiotherapist for the club and author of the Wakefield Trinity Heritage website has researched Mr Coetzer’s history extensively.
Mr Robinson said: “Gert was not just a speed merchant there were faster wingers in the game, but his determination brought him many tries, and his strong defence was a lesson to others.
“He was difficult to tackle with his side-stepping skills and he never knew what it meant to be beaten in his quest for tries.
“Many who saw him still remember him tip-toeing down the white line on the left wing on his way to the line, with ‘Oupa, Oupa’ echoing from chants on the terraces.”
Mr Coetzer played for the Johannesburg Celtic and Bloemfontein Aquilae sides in his native South Africa and first came to light playing against the touring Trinity team of 1962.
Mr Coetzer was instrumental in Trinity’s championship winning teams of 1967 and 1968, contributing 43 tries. He played as Trinity defeated St Helens in 1967 after a replay, and when they retained the championship in 1968, defeating Hull KR.
His last game for the club was the 1968 “Watersplash” cup final against Leeds at Wembley.