"We found it in my grandfather's garage 50 years ago when we were cleaning it out. A photo was taken of him in it not long before he died.
"Ever since we've really kept it in the family, but this year we wanted it to have a wider audience. We're obviously pretty disappointed and we can't understand why it's happened. It's not something you can put on TradeMe, it's not something you can wear."
The family didn't blame the NZRU and hoped for its safe return.
NZRU chief executive Steve Tew said the jersey went missing during preparations when catering and events staff were in and out of the centre.
"We clearly didn't have enough security in place. It's not the first function we've held, but it is the first time people have let us down, so I guess we'll have to review it."
The theft means the NZRU is also assessing how it shares other memorabilia with the public.
"There's nothing worse than a trophy that spends its life locked in a cabinet. We want our treasures to be touchable and out among our people. It makes life harder."
Mr Tew said the union had hoped to recover the jersey through informal inquiries. Those had come to nothing, which is why the public appeal was launched yesterday.
The distinctive black jumper has a red band and enlarged silver fern. It also looked its age - with a number of obvious holes, it was in a fragile condition. The Small family had intended to start preservation work after the series.
Rugby historian Malcolm Mulholland said the jersey was possibly the oldest surviving in Maori rugby history as many from early decades were buried with players. The next batch of surviving jerseys dated from the 1940s and 1950s.
SPORTING ICON
* Police are appealing for information about the theft of a 100-year-old New Zealand Maori rugby jersey.
* Belonged to the family of David Small, a member of the 1910 touring side to Australia.
* People can call the police directly or Crimestoppers on 0800 555 11.