Faint signal leads treasure hunters to massive discovery at legendary 400-year-old wreck

The ingot was found by divers with Mel Fisher's Shipwreck Expeditions at the wreck site of the Nuestra Señora de Atocha, about 35 miles west of Key West.

Mel Fisher began searching for the Atocha in 1969. He spent years recovering artifacts from the wreck before his company prevailed in a lengthy legal battle over rights to its treasure in 1982.

Fisher's team discovered the Atocha's famed "Mother Lode," or main cargo deposit, in 1985 - and the site still yields new finds decades later.

In an August press release, Mel Fisher's Shipwreck Expeditions said the ingot has an estimated value of about $18,000 to $25,000.

Captain Drake Nicholas was retracing an area from the salvage vessel DARE when his metal detector picked up a faint signal, he told Fox News Digital.

The captain said he was following a "tight trail of coins" at the time.

"Faint hits are always the most exciting because they lead to, you know, stuff very deep in the mud," said Nicholas.

"And I got that very faint hit. I dug down like I always do ... and it got louder, and that's, you know, when the excitement really kicks in."

"I was so excited," he said.

"I thought it was a cannon, but it ended up being a copper ingot, which was also very exciting."

"I believe that only certain people could actually own copper because it was making such strong cannons," he said.

"It wasn't something [that] an everyday guy could have a stockpile of - it was more for the king and queen to make cannons."

To make the ingots, metalworkers "would basically dig a hole in the sand and just pour copper into it," he said.

"It would make this copper ingot or a copper bar," added Nicholas.

The recent discoveries have given Nicholas reason to believe the crew may be closing in on a larger concentration of treasure.

"The size of what we've been finding lately is … leading us to what I believe is the rest of the treasure," Nicholas said.

"We've never really [gotten] to penetrate that mud with a metal detector to get down and find, you know, the rest of the silver bars, copper ingots and coins," he said.

"Right now, I have 19 targets that are very interesting, very high-value targets that I'm going out after next," added Nicholas.

"And it's a lot of digging through that mud and getting down to that level. But once I'm there, I'm very, very confident and excited - we're just very excited to see where this is leading."

The latest discovery follows another recent find from the Atocha shipwreck.