Denis,
This is from the Jerry Jones website:
Q. Where do I find my serial number?
A. Mid 1988~to~mid 1990. Serial numbers hand lettered in black ink at lower back of headstock. Black or dark colored instruments may be numbered inside control cavity or backside of white pickguards. Some in neck cavity.
Mid 1990~to~mid 1993. Silver and black serial number labels applied to top back of headstock.
Mid 1992~to~late 1998. Serial number engraved on metal jack plate. Models without jackplates have s/n engraved on lower edge of bridge. Sitars engraved number is located on metal string guide at rear of bridge.
Jan 1998~to~current. Printed white label inside control cavity…all instruments. First two digits indicate year of production.
Hope it helps. Good luck.