J Mascis - Jazzmaster
J has many Jazzmasters,all from the 1960's, He also has had a '62 blue/tortoise pickguard, '65 Lake Placid Blue/white pickguard and '59 blue/gold-anodized pickguard.
This is his first Jazzmaster, that he said that he got for $300 at "Slimy Bob's Guitar Ripoff Shop". It is a sunburst covered in stickers and has Grover tuners installed, and was used on the first three Dinosaur Jr albums.
He uses his signature Jazzmasters on stage now, along with a couple of vintage sunburst Jazzmasters.
1965 Fender Jazzmaster - Sunburst