The experts and analysts made their determination by studying high-definition photographs of a North Korean military parade held July 27.
NBC News space and missile expert James Oberg, who witnessed North Korea's failed Unha-3 rocket launch in April 2012, pointed to the "undulating skin" seen on a warhead as evidence that it was bogus.
The skin on that part of a long-range missile needs to be very smooth to prevent turbulence and also to keep the missile on course, Oberg said.
Furthermore, no evidence of crucial "retro rockets" was seen on the Hwasong-13, according to aerospace engineer and former RAND Corp. military analyst Markus Schiller. Retro rockets are necessary for intercontinental ballistic missiles (ICBMs) like the Hwasong to reach altitudes needed to strike far-off targets, NBC reports.
This isn't the first time that experts have asserted the Hermit Kingdom's missiles are just mock-ups. In 2012, the New York Times reported on a paper by two German missile experts (one of them was Schiller) that named several reasons why the North's ICBMs were just show-ponies. The paper, published on armscontrolwonk.com, noted that there is still no evidence that North Korea has a working ICBM in its possession.
Still, even on top of reports that construction has halted at one of North Korea's major rocket launch facilities and that one of its top government missile experts has gone missing (some say he may have been purged), it may be foolish to underestimate North Korea's military capabilities.
In December, a joint U.S.-Canadian aerospace organization confirmed the North's claims that it had put a satellite into orbit using a three-stage rocket that was said to be similar in design to one that could carry a nuclear missile as far as California. In February, unusual seismic activity in northeastern North Korea was thought to be evidence of an underground nuclear explosion, which would be the country's third nuclear test to date.
Furthermore, it's important to remember that even if North Korea can't hit the mainland U.S. (yet), it can still strike countries with U.S. military bases, such as Japan and South Korea.