The fragment of Moy Hall plaid has been given to the Scottish Tartans Authority on long term loan after it was purchased by a supporter of the organisation.
The tartan cloth, which measures around 30 centimetres wide, was given by Bonnie Prince Charlie to Lady Anne Mackintosh who raised a Jacobite regiment during the 1745 rebellion despite being married to a captain in the British forces.
The tartan was widely copied during the 19th Century given its Jacobite connections with the authenticity of many fragments debated over decades.
The recently acquired piece sold for £3,000 at Lyon & Turnbull in Edinburgh during the summer after the successful buyer saw off competition from overseas bidders to secure the remnant.
The STA is satisfied that the fragment is an original and said it was “delighted” to be able to retain the piece in Scotland.
Peter MacDonald, tartans expert at STA, has spent more than 20 years researching the cloth given by Charles Edward Stuart to Lady Anne following his stay at Moy Hall near Inverness in February 1746.
Lady Anne, who was arrested following Culloden and held in Inverness Prson for six weeks, later cut the plaid into keepsakes and distributed them to her friends.
Mr MacDonald said the fragment now with the STA was one of six confirmed pieces of the original plaid, including the one that remains at Moy Hall.
Mr MacDonald said: “Other than the piece still at Moy Hall, this new find is the largest known surviving specimen of the original plaid.
“My research has identified a unique threading arrangement in the original Moy Hall tartan cloth, a feature that can be clearly seen in the Lyon & Turnbull piece, thus verifying its provenance as a section of the original.”
A further 11 fragments - some which are on show in museums around Scotland - purport to be the Moy tartan but Mr MacDonald believes a number may be taken from later copies of the cloth.
A number of signature elements in the Moy Hall plaid - including a herringbone selvedge which contains a slight flaw - has allowed Mr MacDonald to determine which pieces are from the original plaid and which have been taken from 19th Century replicas.
Mr MacDonald said the original plaid would have been nine or 10ft wide but that only the equivalent of an A4 piece of paper is known to survive.
“That is remarkable. Most pieces of tartan of that period did not survive. The fact that these did survive is due to their cultural significance and their links to the Jacobites. That is why they were kept and preserved.
“The copies were made at the height of the Highland revivalism and really manufacturers were looking around for anything that was original.”
The copied plaid became known as the Culloden Coat.
Mr MacDonald said there was almost nothing know about who made the original plaid gifted to Lady Anne.
It would have been regarded as “cloth of stature” given it is predominately red in colour, the most expensive dye of the day which came from crushed insect shells from Mexico.
“The more red you have, the bigger the statement you are making,” he added.
It is hoped the Moy Hall plaid will become a key exhibit at The National Tartan Centre which is being planned by STA for a site in Stirling. Plans are at the development stage.
John McLeish, chairman of Scottish Tartans Authority, added: “It is incredibly exciting to work with such an iconic specimen that has a direct connection with one of history’s most romantic figures.
“We are delighted to have been involved in retaining this important artefact here in Scotland and this adds a real boost to our plans to establish a National Tartan Centre in Stirling by 2020.”