In response to Saudi Arabia’s biggest-ever war game, in early May Iran’s revolutionary guard hosted its biggest-ever arms bazaar. The highlight of the show was a private presentation for supreme leader Ayatollah Ali Khamenei featuring Tehran’s copies of the U.S. RQ-170 Sentinel stealth drone that Iran captured near the border with Afghanistan in late 2011.

The presentation revealed many of the secrets of the wing-shaped spy drone—and also recounted Iran’s methods for capturing the robot … and reverse-engineering it.

At the presentation for Khamenei, Brig. Gen. Amir Ali Hajizadeh, the head of Islamic Republic Guard Corps Air Force, announced that an Iranian-made 1:7 scale model of the Sentinel has already flew—and that a full-size copy would perform its first test flight in four months. That is, no later than September.

Iranians first encountered the Sentinel in the autumn of 2007, west of Isfahan, according to the presentation.

Iranian fighters scrambled to intercept the mysterious object. Isfahan is the main base for Iran’s American-made F-14s, and also boasts the country’s first counter-stealth radar, the Chinese JY-14.

The briefing for Khamenei included what appeared to be military electro-optical footage of an RQ-170 in flight. The footage purportedly dated back to 2009, and seems to prove that Tehran was capable of tracking the Sentinels two years before it captured one.

The RQ-170s flew from NATO’s Kandahar airfield in southern Afghanistan starting no later than 2007, and from the United Arab Emirates in 2010.