Optimizing scanning images from 1800 - 1900?

[Jim - Fine Art Lens]

Looking for a work flow to optimize the images that I am scanning from the late 1800 and early 1900s.  Our technologic state amplifies the printing limitations from the era.  Would prefer to smooth out the dot patterns in pre or post production.  TIA 

[Stephen Marsh]

General advice based on modern prints:

Start by doing as much as possible during scanning via the scanner (highest optical resolution), scanner software (moiré reduction option) and or rotating the original on the glass by 15 degrees or whatever you decide is best (a cardboard triangle wedge "jig" can be made for consistency).

3rd party FFT filters may also help as the first step before other post processing is performed. 

In post, rotate back and resample down to the required resolution.

Another option is to consider using a DSLR in a copy stand with appropriate lighting instead of a scanner.

I don't have any first-hand experience with old prints which may be different, so YMMV. Good luck!

[Semaphoric]

That doesn't look like a line screen; more like a texture applied when  the print was hand-colored.

Here's a quick test using Surface Blur:

Some areas, like the foliage and the trusswork of the airship, I masked out the effect, since the dots were less noticeable there, and could use a little sharpness kick.

The underside of the gas bag envelope looks like it could be a real bear.