Ebay is your friend.  Search on completed auctions and ignore ones where no
one bought anything.  But none of it is worth much these days.

   Both methods previously recommended will help you determine current value,
but not necessarily accurately, as condition is paramount and eBay can't hold
a candle to KEH in determining condition in my experience. eBay has a greater
fluctuation in prices due to the nature of auctions, while KEH is the
industry standard in grading of used items. I have personally received some
C330 items from auctions that would not have even passed KEH grading, so for
that reason I recommend KEH. I am not an agent of either KEH or eBay, just
sharing my experiences.
   As for the "Sports Finder" you mention, I believe you are mistaken in the
nomenclature. The "Sports Finder" is built into the waist level finder hood.
I believe you may be referring to the Porrofinder which as I understand it
uses mirrors to orient the image in the viewfinder correctly. My Prism Finder
image orientation is upright but still backwards right to left when reading
the data off the focusing screen. Hope this helps.

Silver-and-Silicon.

The PorroFinder, is that what you mean?  Those aren't worth a lot.    The
prism finder is more desirable, and those go for about $150,  if you are
lucky.

Patrick