Mr Paul, a society veteran, said many hours had been spent to give B10 that special gleam for a weekend of celebration for their pint-sized steam locomotive.
B10 was built in England in 1924 and imported for North Island railway construction work under the former Public Works Department.
It eventually came south to Otago in 1930, where it was acquired by Milburn Cement.
The Pukeuri Freezing Works acquired it in 1967 and Oamaru Steam and Rail took ownership in 1997.
Today the official centennial will be celebrated at the Oamaru Harbour railway precinct and will continue through the weekend.