I like the Mamyia loupes: http://www.mamiya.com/
Visit my website at www.ArtLiem.comor my online portfolios at APUG and ModelMayhem
Here is a truism concerning loupes: When dropped, expensive loupes are irreparably damaged but cheap loupes always bounce.
The last conversation my wife and I had about loupes went something like this:
"Oh, Lee, I knocked this off the light box. Do you use it?"
"No, Martha. Not anymore."