(CNN) The first military parade held by North Korean dictator Kim Jong Un, shortly after he became leader, was mocked by experts as a "dog and pony show."

But five years later, as the country appears to be preparing for another such display, things seem a lot more serious.

North Korea is expected to mark the birthday of the country's founder Kim Il Sung on Saturday with a military parade.

As the country celebrates the "Day of the Sun," the world will be watching closely for any information that can be gleaned about Pyongyang's weapons program following a series of missile and nuclear tests

What can be learned?

Markus Schiller, a weapons expert with ST Analytics, said that parades "always involve mock-ups."

"No nation in the world develops missiles and shows the real thing during a parade, it's just too dangerous," he said. "If anything happens, it blows up, right next to the 'Dear Leader'."

a high-profile military parade helmed by Kim Jong Un. That being said, a lot can be learned from what is on display. In 2012, Schiller co-authored an influential report with Robert Schmucker analyzing

The missiles on display demonstrated inconsistent designs and many flaws that indicated they were "more show than real threat," the pair wrote. In particular they were skeptical of a purported intercontinental ballistic missile (ICBM).

"We were quite surprised to see a missile of that size," Schiller said. "What we had seen until then was about one quarter of the size, suddenly they're showing an ICBM."

He warned against taking anything the North Koreans display at face value: "Whenever they've shown anything, in almost every case they've been lying."

This was the verdict of experts in 2015 after another massive parade, showcasing many of the same weapons.

What's changed?

Under Kim Jong Un, North Korea's off-and-on nuclear program has progressed significantly.

Since he took power in 2011, Pyongyang has conducted three nuclear tests , including what it claimed to be a thermonuclear device.

Speaking to CNN last month , Euan Graham, director of international security at Australia's Lowy Institute, cautioned against underestimating the country's capabilities.

"I think a lot of people would have scoffed at the idea that a country of threadbare means like North Korea would be able to test (submarine-launched ballistic missiles)," he said.

But Schiller said there was still room for a great deal of skepticism.

"If you just look at what they showed on TV and in photos, it looks impressive," he said. "But from an engineering and project management approach, a lot of mistakes have been done in the past year."

In an undated photo, Kim Jong Un gathers with nuclear weapons scientists and technologists around what North Korea claimed was a miniaturized nuclear warhead.

What to look for

One problem with the North Korean weapon program that's likely to be on display at this weekend's parade, Schiller said, is its apparently sprawling size.

Previously, mock-ups of ostensibly the same missile -- such as the KN-08, which was rolled out in 2012 and 2015 -- "looked very different," Schiller said. "That would never happen if there is a frozen missile design, you know what the missile should look like."

He also pointed to an incident in March last year, when Pyongyang claimed it had successfully tested a nuclear warhead . In images released by North Korean state media showing Kim celebrating, mock-ups of both the KN-08 and the newer KN-14 were on show.

The KN-14, Schiller and other analysts agree, is far superior to the "old flawed design," and so it defies logic that both would still be in development.

And yet having several missiles for the same purpose is a characteristic of the North Korean weapons program.

"They have 15 different missiles beyond a range of 300 kilometers," Schiller said. The research and development required to produce such an arsenal, rather than depending on one fixed design, would be huge.

He compared the North Korean program with that of Iran: "Iran has a very sensible, strategically defensible program. They put a policy in place, and develop their missiles to meet that requirement."

Many of Pyongyang's missiles are based on Soviet or Chinese designs. The Musudan, one of the most in-house programs, is also perhaps the country's least successful.

"The Musudan's design departures from the Soviet R-27 have reduced the missile's performance in every meaningful criterion," Ralph Savelsberg and James Kiessling wrote for watchdog 38 North last year. All but three Musudan tests have ended in failure, according to 38 North.

"The Musudan is the only one that doesn't work," Schiller said. "All the other missiles work perfectly so what's the reason for that?"

He suggested that other designs may have been bought by Kim Jong Un's regime, or those of his predecessors, thus exaggerating the capabilities of the North Korean weapons program.

"It's a long, long time, it's a long road (to an ICBM), things always take a lot longer than expected," Schiller said.