Sears made the Silvertone brand from at least the 1920's, when they had
mechanical diaphragms and horns and wind-up motors, until at least the
1980's, when they were Japanese.  For all I know the Silvertone marque,
is still going.  So your phonograph might be equipped with a mica horn,
a cactus-spine needle, or with low-noise field-effect transistors, de-
pending on the particular model you have.  Let us know some details.

Another source for information -- and the quality of advice seems to
vary -- is a Usenet group named "rec.antiques.radio+phono."  Type the
name into Google, and it will direct you there.  Sometimes it's really
helpful, sometimes it's a lot less useful than eBay.

And eBay is another good tool.  One of the finer things about eBay is
that you can use it to teach business students the meaning of the
finance term "price discovery."  If you want to know what something
might be worth, hunt for it on eBay.  Even if there's nothing similar
up for auction at that moment, you can see what similar items finally
sold for in the past.  Warning: eBay is a first-class time-sink: you
can get lost for days chasing down everything you've ever thought of
buying or selling.

Mark Kinsler
Lancaster, Ohio