This article is from the RCA SelectaVision VideoDisc FAQ, by firstname.lastname@example.org (Tom Howe) with numerous contributions by others.
This is a disc used in the Thomson transmissive optical disc system, a
contemporary of the RCA VideoDisc system targeted to a limited degree at
the industrial marketplace in the early 1980's. This system is no longer
supported, and it is mere coincidence that Thomson presently owns RCA's
Consumer Electronics Division. This system had the then distinct feature
of having two levels of pits which the laser could track simply by
refocusing itself. So unlike the DiscoVision system in the early 80's,
both "sides" of a Thomson-CSF disc could be played without flipping the
disc over. The system was quite sensitive to dust and fingerprints,
hence the caddy-housed discs.