X-ray
Maybe not technically microscopy but close enough. These units are useful to see packages, HSMs, etc before making cuts.
CSAM might be a good alternative to x-ray imaging
Contents
DIY
Some people make DIY x-ray setups by using "lighthouse" vacuum tubes and using photographic films. Might be able to use an intensifier to make it digital. Could integrate x-ray blotches over time on a CCD? Not fast and small area but might be inexpensive / easy.
Micro Focus
Micro-50: nice smallish unit. Read chamber reported as 14" wide X 14" deep X 13" tall. Probably takes film. Also had on it "MAGNAFLUX X-ray Equipment"
Chip imaging
http:www.emosystems.de/en/dienstleistungen/microct/
Claims 0.5 um resolution, could be used to non-destructively image some old chips
SLAC
http:www-ssrl.slac.stanford.edu/content/science/highlight/2011-09-26/x-ray-nanotomography-imaging-circuit-integrity
http:www.nature.com/nature/journal/v543/n7645/full/543325a.html