I must be starting to forget my technical jargon but wouldn't "dry offset with raised plate surfaces" be equivalent to letterpress or flexo?
Often terms are mixed but this is how I learned it.
Waterless offset uses a non raised plate. No water. Ink is not accepted in the non image area by a silicone surface but maybe could be another material. The point is that it is not a raised plate. The image goes from the plate to the blanket and then to the paper. That is the offset part.
Dry offset (no water) uses a raised image surface on the plate (use to be metal and now often polymer) and the image is transferred to the blanket and then the paper. Dry offset usually is fed with a more conventional roller train and ink fountain.
Flexo has a raised image on the plate ( usually rubber but now also polymer plate) but the image from the plate goes directly to the paper or substrate. No offsetting here.
The flexo plate now is normally inked by an anilox roller but in the past it was inked by form rollers and had a roller train and ink fountain.
Letter press has a raised image on the plate and prints directly to the substrate.
Offset lithography of course uses water based fluid to keep the non image area of the flat plate free of ink. Printing to the blanket and then paper gives it the offset term.
Offset lithography can also be fed with ink from an anilox roller, such as in the Anicolor press instead of the traditional roller train. The waterless version of that would be like the Karat or Genius press.
One could have lithography without the offset where the image is printed right from the plate to the substrate. Not sure if there is a special term for this.
And there can be combinations where a flexo or letter press is offset with a blanket before printing onto the paper.
I would say that the older version of flexo and letter press is very similar but with letter press one can get an added effect with a deeper impression from the metal plate at higher pressures.
Then there is also common blanket presses for offset and common impression cylinders and blanket to blanket versions.
I would suggest that it could be better if people did not think of printing processes as being done with fixed technical concepts of how the technology should work. Think in a more general way. All printing processes aim to put a specific amount of ink in a specific location. Thinking about how to do that in the best way can lead to advancements in printing.
