. . . in your opinion would they use mechanical means to create exact copy after exact copy after exact copy by a means that does take talent? Or at the very least, exceptionally well made machine parts that are skillfully put together?
Let us say that a Legendary Mechanic creates an artifact Clock, with a perfectly even mainspring, a finely tuned pendulum, and gears of the highest quality. Copies of this artifact could theoretically be made, possibly using mass-production techniques as mechanical and artless as casting the duplicate parts from molds based on the original components. But building these clocks from such a "kit" would still be a laborious & exacting process, testing both the physical and mental abilities of even a well-trained Mechanic. In my opinion, dwarves would probably find such a process acceptable, and even commendable--depending on the level of respect that these duplicate Clocks & their makers showed for the original, artifact work & its creator.
While lithography would be super dwarfy based on the fact it's writing on big ass stone plates... it's also way beyond the cut-off date: 18th century, and the cut-off date is the mid-15th century.
More important than when a technology actually
was developed (in Earth chronology) is when it
could have been realistically developed. Velcro is the classic example: It wasn't formally invented until 1941, but it has literally
zero tech requirements. It was inspired by plant burrs stuck to animal hair, and could have been (and indeed, most probably
was) invented in prehistoric times--we could literally have had buttons
before we had clothes.
Lithography requires gum arabic (naturally-occurring tree resin), weak acid (lemons have juice), and smoothly-polished stone (we're dwarves, yo). This creates a "tech feel" of around the 13th or 14th century, and then subtract 100 years or so because it's a stone-based technology, so it would be well within the cutoff period. But, as I said earlier, dwarves would be very unlikely to invent the process because they wouldn't see it as having any value: Even IF they wanted to mass-produce printed material, why the heck would they bother using
acid to slowly etch the stone, when there's a Professional Engraver living right next door?