Green Mountain ($3.40) was having his first start in 42 weeks but came away to beat Great Keppel ($4) by 2-1/4 lengths in a maiden race over 1350m
The gelding cost $500,000 at Inglis Easter Sales and he is a half-brother to the Group One-winning mare Politeness.
Green Mountain had one run at Newcastle before being sent to Dunn at Murwillumbah.
“He is obviously a nice horse and he had a trial and a jump-out to get him ready for 1350 metres first-up,” Dunn said.
“He is owned by Hong Kong interests so whether he ends up there I don't know.
“He will probably need to get his rating up a bit so I should have him for a bit longer.”
Apprentice Jacob Grob had a happy return to riding when Winds Of Change ($5.50) scored a last-stride win.
He returned to Queensland last year but suffered a neck injury in a fall at the Gold Coast on September 15 and hadn't ridden in a race since.
Winds of Change is trained by Robert Heathcote for his friend Neil Owen who mixes training with owning a chemist shop on the Darling Downs.
Tony Gollan and Brad Stewart celebrated being named trainer and jockey of the summer carnival by producing impressive Black Strata ($3.20) a debut maiden winner.
A $110,000 buy from the Inglis sales, Black Strata has been given plenty of time before making his debut on Wednesday.