Heartfield 1988 -1993 Heartfield History
Heartfield guitars were introduced in 1989 and were produced up to 1993 (approximately) in the Fujigen Gakki factory in Japan. Fender used the Heartfield brand name and started producing guitars for the Japanese market there. This resulted in guitars labelled “Heartfield”, “Heartfield by Fender” and even “Fender”. [Source: Heartfield Central ]
Dating Heartfield Guitars
http://www.heartfield-central.com/html/dating.htm
1989 Owners Manual
http://www.fender.com/support/manuals/pdfs/instr_owners/Heartfield_Guitars_and_Basses_Japan_1989.pdf
Heartfield guitar catalogs

http://web.wt.net/~jsilva/hrtfld.html

http://www.heartfield-central.com/ includes forum