Well, as long as there is apparently some interest in this area here, it should be stated that it is not all that difficult to produce authentic-appearing typeset official seals.
As Jim Kotanchik commented in his book, "As part of the research for this chapter, the author spent two days as an 'apprentice' in a print shop... This shop has over 600 different typefaces, including most of those used for the seals described in this chapter..."
Many years ago, so the story goes (according to my fading memory), an experiment was made to create a typeset official seal. I am not sure of the source of this experiment. The result of this experiment is shown below.
The city name was intentionally set to be a) a real city (Google it) and b) a somewhat silly-sounding place to have needed official seals.
Actual typeset (or letterpress) forms were used to hold movable type and rules (or lines). The four forms were set in the similar tete-beche format that other, similar seals were set in. The paper and ink came from 19th century sources. They were entirely designed to appear to be "real."
The light brown "tone spots" were applied (as I recall) by flicking diluted regular tea on them with a small paint brush.
The panes, on various colors of paper and in imperforate and roulette settings, were not mass produced or advertised anywhere, and they were only available for a very limited time. They were not that expensive, and it was "understood" that they were not real, though there is nothing on them to indicate as such. I personally have not seen them offered for sale on any venue for over a decade.
Just something to be aware of, should one encounter an "unlisted" typeset official seal in the future.
As I stated above, the fact that a seal is found in what appears to be a damaged, used condition, with a cancel (even partial), considerably helps to authenticate it as being genuine.
Plus, like with many other obscure areas of stamp collecting, one develops a "feel" for these things over time, and sometimes the fakes are more apparent than the genuine (and vice-versa). This is similar to the several revenue collectors here that can "sniff" out a fake imperf. revenue stamp from a genuine with just a glance.