The “impulse” is the physical impact of the graver point into the metal as it cuts and displaces metal. Craftsman previously only used a chasing hammer for this work. Fine work is extremely time consuming as every linear inch of the engraving is physically driven by hand. This wartime engraving is the perfect example to illustrate the difference as it is far from the finest work and looks fairly crude under magnification, Gustloff had their hands full with other work in 1942 after all. Especially as hard turns are made in the scroll work, you can see every physical impact of the hammer as he worked.
I don’t collect newer stuff so I don’t have an example in hand to photograph, but here’s an example of pneumatic work pulled from the net to illustrate the difference. Under magnification you can see that there is virtually no discernible impulse from one of these tools. The lines and especially the hard curves are especially smooth and fluid. Think of the pneumatic graver as a miniature air hammer with a short stroke, what used to take two hands, now only takes one with this tool, freeing up the other for more control over the work. Long story short, if you see something with supposedly period correct engraved numbering or markings, keep the above in mind as it would date the work to the 1980’s at the earliest. All this is really a side point to the subject, as we know the correct style of numbering for these mounts is done with a pantograph in the first place.