Mr Irwin, who was profiled recently by the Otago Daily Times, said yesterday he had sold his entire stock of 10 tools at the expo and had received orders for dozens more, which would be made by Templeton's Engineering at Albert Town.
The Slammer was one of 68 items in the innovators section of the show, which was won by Lincoln University students James Blanchet and Andrew Begg, with their invention, the Ezzy-K, a K-line irrigation system mover.
Mr Irwin said the show was "very much a dairy farmer's place" but the tool was popular with people working in roading, forestry, tree planting and gardening industries.
"Selling a fancy sharp spade to Waikato dairy farmers with an American accent - I didn't think it was going to happen," he said.
While many of the innovators focused on reducing manual labour, Mr Irwin's philosophy is to make it easier and safer, especially on backs.
"The ones who seemed impressed were the old guys who sat and watched me talk for 15 minutes without saying anything, and then gave that nod that farmers do, then a wink, and would say "Good on you. That's the simplest thing I've seen". They are the hardest to impress," Mr Irwin said.
