There was only one TRD package for the 1st generation of Tacoma--the TRD Off-Road package which includes the electrically-actuated rear locking differential, among other things.
Look on the dash to the left of the steering wheel for a button that says "RR DIFF LOCK". If it doesn't have it, it's not a TRD. The diff lock was available without the TRD package though, so having it doesn't guarantee it's a TRD.
Limited is a different option package. For 2003, it includes: color-keyed front bumper and fender flares, chrome grill surround and door handles, power mirrors, sliding rear window with privacy glass, dual-fabric sun visors, orange-illuminated white-face gauges, power windows/locks, leather trimmed steering wheel and shift knob (manual trans only), intermittent wipers, A/C, driver's power lumbar support and deluxe 3-in-1 AM/FM/cassette/CD with 6-speakers.