This article is from the RCA SelectaVision VideoDisc FAQ, by email@example.com (Tom Howe) with numerous contributions by others.
Some CED's issued late in production have two caddy labels, one glued
directly over the other. RCA prepared an equal number of discs and
caddies, but if some discs were rejected during the visual inspection
step of the production process, there would be some left over caddies.
RCA started to "use up" these extra caddies during the final stretch of
CED production, so the label underneath is for an earlier CED release.
It is also possible that there may be some misprints on the label
underneath. I have one disc obtained from an RCA engineer that has "Cat
on a Hot Tin Roof" in front, and "Oklahoma" on back due to a misprint.
Since "Cat on a Hot Tin Roof" discs had already been loaded into the
caddies, these discs were given away free to RCA employees. But if they
had caught the error while the caddies were still empty, the caddies may
have been saved for eventual relabeling. It's my understanding that RCA
also mis-stamped some discs, so the two sides are from different movies,
but these discs were destroyed at the factory rather than being
distributed among employees.