This image was on a yearly Corvette desk calendar. It is identified as a Corvette XP-856, but I’ve never seen it before. Does anybody know what this is?

This image was on a yearly Corvette desk calendar. It is identified as a Corvette XP-856, but I’ve never seen it before. Does anybody know what this is?

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During my very brief stint at GM Design Staff-I managed to get a look in the photo achives. Over the years there were many Pontiac versions of the Vette done. Could this be one?