According to the beloved
Rebel Scum, the Imperial Sentinel seen in Dark Empire is takenfrom an unused concept sketch for the Emporer's Royal Guard. I can buy that, but it's what they say next that has me scratching my head:
"The
Imperial Sentinel was almost made as a vintage figure named
Altha Prime,, in a series of toys designed to continue after the Classic Trilogy. Altha Prime and his Clone Warriors would have been a new challenge for our heroes, but the line was never developed past conceptual designs."
Is this true??

Granted, my knowledge of vintage figures is overall a bit limited and my knowledge of preproduction figures even more so (though I have heard and seen pictures, IIRC, that they had working prototypes of Chewbacca's family for the holiday special and for some reason a Luke figure clad in long jedi robes resembling Anakin's and Obi Wan's), but I found this quite interesting. If it is legitimate, does anyone have any further information on this unproduced line, or any others?