Chris,
Does anyone know what these are for?
<http://www.mythtech.net/rings.jpg>
The yellow one in the upper left is definitely a write enable ring for a
1/2" tape reel. You could write on these tapes only if a ring like this
was in place before mounting the reel in the drive.
Reels were normally delivered _including_ the write ring, but careful
users would remove the rings to protect their data from getting
accidentally overwritten, so you usually had a lot of spare rings at
those times. I worked in a computing center where we would sometimes
throw these rings after each other just for fun.
I have about 2 dozen of the yellow ones, and 5 or 6 of
the orange ones
(although not all orange, some are white/clear).
No surprise about the yellow ones. I also have a couple of dozens, in
red, orange, and yellow. What the others are, is unknown here. Maybe
similar parts for a different, perhaps proprietary reel type.
Andreas