Thanks for all the comments!
The Skink pinholes are real pinholes. The Skink zone plate and zone sieve disks, however, are microdot quality printing onto a film substrate. This photo was made with the f/71 Zone Sieve disk.
Sensor dust is something to be aware of, but with ANY f/47, f/71, f/127 or f/219 pinhole you're going to see some dust no matter what. Such small apertures will highlight even the most microscopic dust particles on the sensor stack. There are at least 20-30 spot cleanups in this image (very easy to do with Lightroom), and that's on a recently cleaned sensor. Those spots simply are not visible at f/16-f/22, or any larger lens opening, in normal use.
When you're doing pinhole work, you learn to live with and clean up dust spots... It's a fact of life. I don't worry about it. 🙂
With most DSLRs, the best you can achieve is about a 40mm pinhole due to the mount register and swinging mirror.
G