A whitebox is great for jewelery, but perhaps not for coins.  No
contrast, no shadows, no *detail*...

Perhaps the best lighting for coins, IMHO, is the combination of
a ringlight and another off camera flash.

That is true.  Though, if one wants to really get up close on
small coins a DSLR is much more versatile.

Any old ringlight (triggered by an optical trigger perhaps) and
any old variable power flash (the more variable, the more
versatile) will provide too much light!

Some time back another person asked about the difference in lenses
and lighting for coins, and I made some comparisons and posted it
on my web page

   http://www.apaflo.com/floyd_davidson/dime/

The most immediate conclusion one could draw from it is that a
ring light is much better than a lightbox, for coins.  The next
conclusion is that you don't need an expensive lense to get good
images of coins.  A bellows or set of extension tubes can do
just fine with various lenses that cost less than $30 and
produce result comparitable to really top quality optics.  The
money buys conveniance, not image quality.