Officially, the EX 3 is almost the same as the EX 2, including the highly figured maple top and rosewood fretboard. The differences are that the neck is always set (i.e. glued, not bolted on) and that it has a Heartfield EX tremolo.
This model was introduced in 1989 and discontinued in 1993. It used to sell for $1329.99.
It is pretty much believed now that the EX 3 model never existed and the EX 2 always had a set neck.
Heartfield part number, officially: 031-1400.
Heartfield colour codes available for this guitar, officially: Autumn Gold (529), Antique Burst (537), Crimson Stain (538) and Ebony Stain (539).
First documented month of manufacture: Probably never. It never even appeared in Fender Frontline Magazine.
No pictures, obviously...