As previously announced in
this thread, it seems that a FOURTH surviving example of a MiG-9 aircraft has been discovered in Beijing, China. All of the literature I've referenced, and all of the people I've come across who know of these things, all concurred that there were only three known surviving examples, so this may be an important find.
While I was in Beijing in May of 2011, I happened to notice what at first appeared to be an airplane graveyard in a parking lot outside the window of my room at the Vision Hotel:

I was surprised to see the U.S. and other non-Chinese aircraft, but apart from the P-47, the T-6, and the Harrier, I did not try to specifically identify the aircraft until recently. With some assistance from a member on DeviantArt, I identified one MiG-9 on the lot [inside red rectangle] (no. 86104, one of the three known) as well as what appeared to be a partial fuselage of a second MiG-9 [inside red ellipse].
The literature and recent photographs identify the surviving MiG-9 aircraft and their locations as:
1) MiG-9 "01" (a.k.a. "Red") is at the Central Air Force Museum in Monino, Russia, near Moscow (photo from Wikipedia)

2) MiG-9 "30" (a.k.a. "White") is at the Chinese Aviation Museum at Datangshan in Beijing, China (photo from Paul Hannah, posted by Vagabond in the earlier thread)

3) MiG-9 "86104" is at the Beijing Air and Space Museum at Beihang University in Beijing, China (photo from Aircraft in Focus, reference posted by k5083 in another thread)

Prior to being restored and put on display, 86104 was one of the two MiG-9 aircraft on the parking lot. Even though the paint is badly eroded, the number "86104" is still faintly visible over the three color swatches:

But if the other two MiG-9 aircraft were known to be elsewhere at the time this photo was taken, then what is the other one?

Photos from other enthusiasts help confirm its identity as a MiG-9:
(posted by Lightjug, September 2012)

(also posted by Lightjug, September 2012 - the MiG-9 is partially obscured by another fuselage)

(Paul Hannah, taken in 2007, posted by Vagabond July 2015)

So a FOURTH surviving example of a MiG-9 does seem to exist, probably owned by the Beijing Air and Space Museum or by Beihang University. While the fuselage, tail, intake, and other details match, it is the intake-mounted 37mm cannon that is the giveaway, as no other aircraft had that configuration.
The task now is to attribute it. According to various sources, there were a number of prototypes, both original and variants built from production models. Some of these variant prototypes were never completed. There may be a real possibility that this fourth MiG-9 is one of these prototypes. It would make sense that either the University or the Museum would want a second model that is different from their primary exhibit model in some historically or technically significant way. Given its present condition, it may take a real expert in MiG-9 aircraft to identify it, though.