Spotted on Ebay:

G1 Transformers Headmaster Autobot Fortress Maxmimus from 1987

original 1987 TRANSFORMERS Headmaster Autobot Base FORTRESS MAXIMUS. This heroic autobot transforms from robot to battle station to city and back! This auction is complete with original sytrofoam packing material, box and accessories. It has a working elevator, jail cell, and vehicle launchers. Cerebros transforms into the head of Fortress Maximus and Spike transforms into the head of Cerebros to reveal his tech specs highlights.
G1 TRANSFORMERS Headmaster Autobot FORTRESS MAXIMUS '87 - eBay (item 280308331381 end time Feb-08-09 18:09:00 PST)