Keep in mind that most of the 11 foot miniature was repainted by the the Smithsonian before it was ever displayed and before those photos were taken. As far as we know; no documentation of the original condition (and paint job) has made it out into the public domain other than the uncrating photos. The top of the saucer is the ONLY part that has never been repainted since the filming of the show.
In the above photos it shows no pencil lines on the bottom of the saucer but we know that they were there on the original before the initial restoration by the Smithsonian prior to it ever going on display. I don't believe the secondary hull ever had any lines on it but it could in fact have had some very faint pencil lines; there is just no way of knowing.