Zenith TV question

[radiotvnut]

This may sound foolish; but, does anyone know the actual year that Zenith introduced the upright, fold down solid state Chromacolor II chassis? I figured '73 or '74; but, don't know for sure. I remember finding a 19" CCII many years ago with the fold down chassis that had instant on and an ATG (auto tint guard) button where the chromatic button is found on most versions. Could this have been an early version upright chassis?