The son of late Chartist mural artist Kenneth Budd will donate his father's working drawings of the mosaic to Newport.
Oliver Budd has made a miniature version of the artwork, which will be unveiled on the outskirts of the city.
The 58-year-old said there was a chance he would then hand over the full-size charcoal drawings to the museum.
The unveiling of the mosaic at Rogerstone on Monday comes on the 180th anniversary of the Newport Rising.
"I've got all dad's full size Chartist drawings," he said. "I could hang them all up and you would have the full sized Chartist image.
"I've always said I want to give these to the city. A nice time to do it would be with the unveiling.
"I thought at the same time I would bring the original drawings to the city and give them to the museum, where they could archive them.
"They probably have quite a value to them now."
Oliver said his father's drawings were "brilliant".
The original mural was 196ft (60m) long. The figures within them were life size.
Many of the figures were based on Newport councillors. Oliver appeared in it twice - once at each end.
"How do you sell bits of art to the council? You put some councillors in it," he said.
His father had a special way to stop his charcoal from smearing on the paper.
"He would borrow mum's hair spray to fix it so it would not smudge," Oliver said.
"It made the studio smell nice as well."
He joked his mum's hair "was terrible for months".
The Chartist mural was not the only work Kenneth Budd did in the city.
One depicts the Monmouthshire Railway and Canal Company and its role in Newport's growth and prosperity in the 19th Century. That was later restored by Oliver.
Others, created by Oliver and his father, depict market life. All are located at Newport's Old Green Roundabout.
The latter have been wrecked by vandals.
Kenneth Budd would "be spinning in his grave" if he could hear news of the damage, his son said.
Oliver had "never seen graffiti like that in Newport" before.
"We used to have a biennial after-care scheme with Newport City Council," he said.
"We would go down every two years and give a little report and they would either act on it or they wouldn't. But there is no money anymore."
He dubbed the defacing "shocking" and "tragic".
"The people of Newport must be upset about it," he said.
"It's not a nice environment."
The council needed to "get your finger out" and clean it up.
"It's just depressing," Oliver said.
"Newport's had so many ups and downs since I have known it. It has had times when it has felt like it was going to bloom and then it has been dragged back down again."
It was "extraordinary" most of the graffiti surrounded his and his dad's work rather than being sprayed on it.
He was unimpressed the council had done nothing about the damage.
"They should be embarrassed by that graffiti, it's terrible," he said.
"Would you really want a visitor to your city seeing that?"
Newport Council has been asked to comment.