A custom-made railway carriage for Arnott's biscuits has been painstakingly restored for over three years and is now displayed at the Train Works rail museum in Thirlmere.

The decade was the 1960s and the Arnott's biscuit company had switched from tin packaging to the plastic style used today, and they needed a watertight way to transport them by rail.

Not only was NSW Railways keen to transport the biscuits, they built Arnott's 45 custom-made carriages for the job.

"It indicates how important Arnott's was to the railways," Train Works rail museum collections manager Jennifer Edmonds said.

"They were the only company the railways did that for.

"Other companies like Shell took fuel oil and petrol [by rail], but Shell actually owned those tankers.

"The railways felt it was important enough to put their own rolling stock into Arnott's."

With just 45 made, one has now found its way to the New South Wales Southern Highlands town of Thirlmere, home to the enormous Train Works rail museum.

The museum is Australia's largest display of rolling stock and railway objects, artefacts and memorabilia.

An Arnott's van in disguise

PHOTO: The Arnott's biscuit carriage restored by the Train Works museum in Thirlmere has been stacked with traditional Arnott's biscuit flavours for added authenticity. (ABC Illawarra: Justin Huntsdale)

Painted gun-metal grey and with minimal signage, you could be forgiven for not realising it was a carriage for Australia's most iconic biscuit company.

"When I found out we weren't going to be painting it red and putting a parrot on it, I was a bit disappointed because I thought 'what a showpiece'," Ms Edmonds said.

"It's pretty plain and has white writing stencilled on it [ABV - Arnott's Biscuit Van], but the signage was removed by the railways early on because they found when it was parked, the vans got broken into and the biscuits got stolen.

"They removed it quick smart so the general public didn't know what was being carried."

The van was taken out of service in 1976 and the body was removed from the chassis.

The top of the carriage was then sold to the Sydney Tramway Museum at Loftus where it was used for storage.

When the museum no longer needed the carriage, it was offered to Train Works in Thirlmere, where a team of volunteers spent three years and more than 3,000 volunteer hours restoring it to its former glory.

"It's another interesting thing for people to look at, but it also shows people in New South Wales the volume of traffic the railways used to carry," Ms Edmonds said.

"People know they carried coal, grain and wheat, but they normally associate biscuits with the bright red trucks on the road.

"For a long period of time the railways carried these fragile products."