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Mr Lyon, of Peter Lyon Shearing, said Ian Kirkpatrick, of Gisborne, and Andrew Hore, of Stonehenge Station, Patearoa, had confirmed they would speak at the reunion, which would be held on March 15, 16 and 17.
He said he and his wife Elsie had been in business for 33 years and employed between 400 and 500 people a year.
As this year marked a third of a century in business, they thought it would be something to celebrate.
''Fiona McArthur and Bronwyn Bugden worked for me in the 1980s,'' he said.
''They wanted a reunion and put it out on Facebook they wanted to have a get-together, and it started from there.''
He thought there might be a few people interested but about 200 past and present workers had indicated they were coming
''We then thought we might as well make a fist of it.''
He has now hired a marquee that could accommodate about 400 people for the Saturday evening dinner. Daughter Juliette, who is a school teacher, is taking a month's leave from her job to help with the organisation.
They are keen to hear from as many former and current workers as possible, and will invite farming clients, suppliers, support services providers and wool reps to attend the Saturday evening function.
Mr Lyon said he was looking forward to having two All Black greats together at the function.
''Ian Kirkpatrick was one of the great All Blacks and he was also a farmer.''
He said in those days - the 1960s and 1970s - All Blacks worked during the week, largely on farms, where they did much of their training, and played rugby at the weekends.
That is in contrast to the present All Blacks who are professional athletes and train in gyms rather than paddocks.
Hore captained the All Blacks against Canada at the 2011 Rugby World Cup and has worked on his family's Stonehenge Station since his retirement.