Nuke watchers debated Wednesday whether the secret nuclear weapon discussed in Bob Woodward’s new book about President Donald Trump is the W76-2 low-yield warhead.

According to a leaked passage from the Watergate journalist’s soon-to-be-published book, Rage, Trump told Woodward in an interview, sometime between December and July, that “I have built a nuclear — a weapons system that nobody’s ever had in this country before.”

The Washington Post, where Woodward is an associate editor, obtained an advance copy of the book and reported on that passage Wednesday, as did other media outlets.

According to the Post, “anonymous people later confirmed [to Woodward] that the U.S. military had a secret new weapons system, but they would not provide details, and that the sources were surprised Trump had disclosed it.”

A few nuclear-weapon watchers quickly guessed that the secret weapon to which the commander-in-chief referred was the W76-2 low-yield warhead that was deployed in December after a production run that began in 2018. The Trump administration approved the submarine-launched ballistic missile warhead in its 2018 Nuclear Posture Review, which was written mostly in 2017, right after Trump assumed office and years before Woodward’s interviews for Rage.

“My guess is that Trump told Woodward about the first deployment before it was made public,” James Acton, co-director of the Carnegie Endowment for International Peace’s Nuclear Policy Program, wrote on Twitter.

Paul Sonne, a Washington Post reporter covering defense programs, wasn’t so sure.

“If it were the W76-2, it doesn’t make sense the people Woodward confirmed its existence with would be surprised the president shared it,” Sonne Tweeted in response to the speculation.

Introduced generically in January 2018 as part of the Trump Nuclear Posture Review, it took only about a month for the National Nuclear Security Administration to confirm speculation that it would create the warhead on the same production lines then being used for the W76-1 program, which refurbished the full-yield version of the weapon.