"We knew it was an object of significance, but we've got the Bledisloe Cup and Rugby World Cups and the Ranfurly Shield, and it has just slipped through the cracks.
"Eden Park is a rabbit warren. I've been here for four years and yesterday I found a new room. There are probably others I still don't know about."
The cup and base had become separated and did not look like a good match - one reason why it remained unrecognised. The lid is nowhere to be found.
The trophy was presented to the 1924 All Black 'Invincibles' by a group of New Zealanders living in the United Kingdom.
Eden Park believes the 60cm high trophy may have been in storage for about 37 years. Other memorabilia was uncovered including a George Nepia jersey.
The Loving Cup was awarded for the North v South games from 1925 to 1932, and Brown said he hoped it might be used for the revived fixture if it goes ahead this year.
"How serendipitous is that?," he said.
St George is "delighted".
"I half expected it might have been destroyed or melted down during the war, which they did with a lot of silver," he said.
"It couldn't have worked out better."