Full frame (slight trim of edge streaks caused by camera sag). Darkening of the corners is vignetting.

Following is an assortment of 100% crops from the above. These have been "sharpened to taste", which turned out to be Photoshop's unsharp mask at 1 pixel, 100%.
Edge above center:

Near center:

Lower right corner:

Edit: as of 2015-09-09, the Nikon CFI BE 10X, part number MRN70100, can be obtained from SEO Enterprises in Lakeland, Florida, by contacting them through their web page at http://www.seoenterprises.com/shop/help ... =contactus .
In years past, the Nikon CFI 10X BE was advertised by Optics Planet at http://www.opticsplanet.net/nikon-cfi-b ... copes.html, and a corresponding offer at Amazon, for example at http://www.amazon.com/Nikon-Objectives- ... B0048JGVJS (no longer functioning) In both cases the pictures of the objectives were not correct. What they showed were the CFI60 series with 25mm threads, 60 mm parfocal distance, and a larger field. The BE's have a completely different appearance and are DIN -- RMS threads, 45mm parfocal, and a smaller field that is nonetheless large enough to be pushed as shown here.
By the way, this image will be the first one shown in the photography session at an entomology conference coming up in a couple of weeks. I'm going to convert it to monochrome, imply that it's SEM, then put the color back and tell 'em how it was really made. Should be fun!
--Rik
Edit Dec 16, 2012: to add part number
Edit Sep 09, 2015: to update supplier information