Initially released in July 1988 with 3 models per box, RTB12 only contained a single model. The parts are shown in the 1991 catalogue here.
RTB4 Rhinos - WD102 (Jun 88)
RTB4 Rhinos - July 88 Flyer
RTB4 Rhinos - WD103 (Jul 88)
RTB12 Rhino - WD117 (Sep 89)