Just my two cents..I haven't studied this prop nearly as much as you guys, so my hat's off to all of you. But between the Lucas Archive animatronic Idol and the screen-used animatronic Idol there appears to be some discrepancies. Like for example, if it were cracked during filming the crack should be still present / visible on the Lucas Archival version. And also the noticeable difference in the finish of the prop then vs. now, softer details etc.. The seam is also 'very' prominent on the Lucas version as well, whereas in the film it is not. The teeth seem a bit odd/different too between the two Idols (possibly), but could be an optical illusion.
Also note the lighting angle and the clear shadow cast downward from the crack and/or possible panel line as seen in the above photo. It's possible that the shadow is creating the illusion of another seam rather than actually being a seam.
Are these known to be two different versions of the animatronic version of the prop at all?
-Carson