Fender 2007-09 J Mascis Made in Japan Signature Jazzmaster, in Purple Sparkle, with Gold anodized pickguard. - This model predated the Squier J Mascis release.
Used for slow (2008-2018)
Likely a gift from J Mascis to Kevin. It appears Kim Gordon was probably also gifted one as she began using the same model in Sonic Youth live shows around this time too.
Suprisingly, Kevin kept the Tune o' Matic bridge on this guitar, rather than swapping it for a classic vintage style bridge.