Cobain can be seen playing a 1950's Kay P4 Archtop in a Blonde finish through out the music video for "Come As You Are".

This guitar was personally owned by Cobain as it was seen in Cobain's house in the 2011 documentary "Montage of Heck", around 1 Hour and 22 Mins in. The footage is thought to be from 1991 when Cobain was living with Courtney Love in Los Angeles.

Based on some photos that were published, this guitar is thought to be kept in the secret "Kurt Cobain Vault", an unspecified place somewhere in Seattle that has some of Cobain’s old belongings, including a few of his guitars.

In these photos, the Headstock isn't attached to the Neck anymore, which means that Cobain most likely smashed this guitar at some point.

During the filming of the "Come as You Are" video, apparently, there were two Kay P4s on set. According to Joseph Uliano, who produced the video along with Kevin Kerslake, one Kay was left in storage after the video was done and was kept there until recently.

"I produced the video with Kevin Kerslake in the early ’90s and Kurt used this guitar in the video, even though, evidently he has another of that model. […] This could have been a prop as Kurt left it behind on set. Which is where I got it, from the art director."

It’s hard to tell which Kay actually used during the filming. Some signs seem to point towards the same Kay photographed in the "Kurt Cobain Vault", while other signs seem to point towards the newly discovered second Kay.

The first noticeable difference between the two guitars is the fact that the "Vault" guitar has the Kay logo inlaid the pickguard, whereas the second one doesn’t. It’s important to point out here that the guitar used for the video, appears to have no logo on the pickguard, so the second guitar is most likely the one that was used.

At first glance, it looks like the mystery is solved, but when you dig a little deeper and look at the woodgrain on the maple top, you start to notice something.

It appears that the woodgrain of the guitar used in the video matches fairly well with the guitar that was photographed in the "Vault". The only thing that doesn’t match is the pickguard logo.