I have a handful of 4.5" steel disks that play on my Thorens changeable
disc player.  "Helvetia" is printed at the top of the discs, and the
song is on the bottom.  They are all rusted, but that doesn't seem to
hinder them.  How are they different from my other discs, which have
the Thorens name on the label?

Also, I have three Thorens disc players.  One of the older style,
with the brass exposed working, one less old with the more standard
"all in one" movement, and one that is probably newest, that looks
like a gramophone.

My discs don't work on all of them, but almost always work on one of
them.  Well, the middle one started clicking and just stopped working,
even though I had it restored about nine years ago.  Should I try to
get it repaired or just look for a replacement mechanism or whole new
unit?

The other two have been much more temperamental so I don't play them
much.  I have hundreds of discs and like playing them frequently.
I am in the Atlanta, Georgia, area.

Thanks, Penn Jacobs