A rare yellow silk dress with fabric dating back to 1740 will be displayed at Grossmann House in NSW's Hunter region from February, and it has a fascinating backstory.

Fragments of oddly-shaped yellow silk were found in a storage bag in Old Government House, believed to have been donated to the National Trust in the 1970s.

There was no accompanying information about it, but the type of luxurious fabric suggested it was from the 18^th century - a rarity in Australian textile collections.

The pieces of silk were given by the National Trust to the National Institute of Dramatic Art (NIDA) to help conduct research and piece the dress back together.

It wasn't an easy process - the dress was like a riddle and it took days for the team to figure out it had actually been cut and resewn four times throughout its lifetime - likely in 1740, 1770, 1880 and 1940.

It was common practice to remake dresses in past centuries as fabric was so expensive.

The NIDA team, made up of dress historian Hilary Davidson and fine arts costume students Lucy Francis and Jasmin Gray, had to deal with eroded hooks and eyes, pieces that didn't make sense and even some blood spots on the sleeve.

The team ended up making two dresses to show the fabric's varied past - the original silk was hand stitched to the 1770s version, and a cotton-sateen replica was made to show the 1740s version.

Friends of Grossmann and Brough Houses chairperson Holly McNamee said it's a really fascinating story, and this will be the first time the dress is on display outside of Sydney.

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"It's a bit of a mystery dress," she said.

"We're very lucky at Grossmann House that we have a very, very superior textile display room with two fabulous cases that are big enough to take the dress," she said.

The dress is so special that a mannequin was custom made to fit it, and costume expert Lindie Ward is coming to install the dresses at Grossmann House in time for the first open day of the year on Sunday, February 12.

The dress will be on display at Grossmann House, Church Street, Maitland on February 12, March 12, April 30 and May 14 from 10am to 3pm.

Book in for a Grossmann House open day at eventbrite.