Artist Sam Von Mayrhauser of Hartford, Connecticut has tried a bit of everything -- from paintings, drawings, realistic and abstract art.
His brother, Ben accidentally discovered three of his brother's older pieces for sale.
"I happened to drive by this consignment shop, and I saw a painting in the window that looked like my brother's painting," said Ben.
What Ben discovered inside of the shop was a shock.
"That's when I noticed the fake signature and the tag said ‘authentic mid-century Swedish Lillemor Bjork,’” said Ben.
The Von Mayrhauser brothers said they last saw those paintings when their parents were moving out of their Hartford home.
"Somehow I just let those go. I didn't see any value in them at the time," said Sam.
Their moving company brought some furnishings and those works of art -- including a mask self-portrait -- to a local auction house. Bidder number 204 bought the artwork for $110.
Bidder 204 was Sean Carr from Revival Home Fine Furnishings, a consignment store in Connecticut.
“When the auction actually happened, it sold for so little. We acquired it, took a chance to see if we could sell it," said Carr.
Carr said most of his business is consignment, but he buys about 10 percent of the furniture and artwork you'll see in his shop.
“We look and say, ‘What will our customers pay for something like this?’ It's normally between $400 and $1000," said Carr.
Sam's mask self-portrait was presented as a mid-century work of Lillemor Bjork.
In a photo you can see Sam, Ben and their mom standing next to the piece at his college art show in 2009. There's no signature in this shot, but in the shop, the piece bears Bjork's name.
Sam said a large portrait of a naked woman, priced at more than $1000, is his work as well, but NBC couldn't determine if there was a signature on it.
Sam said the third piece is a black and yellow abstract painting.
“Usually an artist will sign the front as part of the composition. In this case, these weren't actually finished pieces; they were schoolwork assignments. My initials were on the back,” said Sam.
"I have the guy take it off the wall with me, and not only does this have a fake signature -- on the back, it has a print out with a bio of the artist who supposedly painted it," Ben said.
Ben took a digital picture which shows Sam's handwrittten initials and a printout from the website 1stDibs.com. That website also shows another painting by artist Kenneth Joaquin, which sold for $4,900.
Revival Home was marketing Sam’s painting -- signed "Joaquin" -- both in the store and online for $1,995.
Kenneth Joaquin lives in San Diego and confirmed to NBC 7 the painting is not his.
"It just felt really strange to know that somebody would copy or do a painting or make a painting and copy my signature onto it. I just didn't understand why they'd even do that since I'm a living artist," Joaquin said.
However, Joaquin thinks he knows what happened.
"My art on 1st dibs, you know, go online and you can find it, and it's -- the prices are varied, you know $4000, $5000 and such,” said Joaquin. “So at that point, they probably saw that, you know, they could throw some scribble on a canvas and throw a signature on there and slide it by real quick. And probably nobody would notice."
Back in Connecticut, NBC interviewed Sean Carr one week after investigating. By that time, he says he'd thrown the three pieces away. NBC asked Carr who changed the signature, signing it Joaquin.
“ I, I, uh, I have no idea,” said Carr. “That's not something we did here. We acquired those. And they didn't sell, and we disposed of them, like we do."
"It wasn't the money because when my parents auctioned them off, “ Sam said. ”I got like $90, and now they're being sold for thousands. It's more just when you work, it's like your legacy. It represents who you are"
RJ Weston of Weston Auctions didn't want to speak on camera. He said he only made about $30 on the sale of the artwork, that he didn't forge any signatures and that he doesn't understand why anyone would take that risk.
"I'm not pointing fingers at anybody. I honestly don't know,” said Carr. “We had them here. We didn't sell them. We didn't manipulate any signatures. I think that's kind of what you're trying to ask me... um, they didn't sell.”
So the question of who changed the signatures on these works of art remains a mystery.
“If you've ever worked on honest day in your life, it's not a good feeling to see these people cashing in on someone else's name," said Sam.
NBC spoke with investigators on both the state and local levels in Connecticut. They say what happened may rise to the level of a criminal offense.
However, they say they would only investigate if someone filed a formal complaint, and Sam von Mayerhauser has chosen not to.