The original cup was a 1906 trophy made by Carrington and Company of London, with a replica created in 1986, a year before the first tournament was held.
Which of the two toured New Zealand was not clear, but tournament organisers said it didn't matter, as they were "equal in stature".
Last month a 27-centre RWC 2011 Roadshow was promoted as taking the William Webb Ellis Cup to the country, and promoters said more than 11,000 New Zealanders had their photo taken with it.
However, news media have reported that the real cup is in Ireland and competition organisers didn't make the distinction between it and the replica public, for security reasons.
Rugby New Zealand 2011 chief executive Martin Snedden said he had contacted tournament owner Rugby World Cup Ltd, a subsidiary of the International Rugby Board, today over the status of the cup.
"We are pleased to be able to reassure all those fans who turned up early in the morning around the country that the experience they had was genuine."
Rugby World Cup Ltd said it possessed two cups.
"As is common with other major sports tournaments, we have two trophies; however, only one is ever used at any given point in time," said tournament director Kit McConnell.
"Both cups are equal in stature. There is no original cup as such, they are interchangeable and we don't distinguish between the two. They were both acquired before the first tournament so share the same Rugby World Cup history.
"Both have been used at past tournaments and both have been in the hands of winning captains and teams.
"I want to reassure New Zealand fans that the cup they have enjoyed recently on the RWC 2011 Roadshow will be the one held aloft on October 23 by the winning captain."
