Although only 4 SMX complete prototypes are believed to have been built, perhaps as many as 15 bodies were made in various design studies as the program progressed. It is possible that the Fuller style car was considered as one of these design studies at Vaughan’s suggestion, considering how many of his ‘design signatures’ appear on the ‘pre-SMX’. Its crude nature, however, indicates a non-running model as opposed to a real completed car. . (Hope I have helped you Bentley T)