While metal detecting at Stroud showground last month, Karuah man Bill Swainson came across a brass button roughly the size of a $2 coin bearing the famous Australian Agricultural Company (AAC) logo.

It is yet to be officially verified but it is believed to be an 1830s convict-era button from the clothing of an AAC worker.

Mr Swainson thought it would be "a nice souvenir" until he showed it to Karuah historian David Benson who told him what a significant find it was.

His enthusiasm was echoed by Great Lakes Council's heritage officer Garry Smith who described the find as "incredible".

The only other known button of this type was found in Newcastle in 1922 and is in the Mitchell Library in Sydney.

"The thing that fascinates me is that it has come all the way from England to Tahlee and up the river to Stroud," Mr Swainson said.

The button is starting to deteriorate and both Mr Swainson and Mr Benson agreed that it would need to go to a museum to be conserved as soon as possible.

"I just want it to be able to be appreciated," Mr Swainson said.

"It would be a shame to lock it up in a private collection where people can't appreciate the history and the links."