Rein - Re-examining my Netherlands and Luxembourg line-engraved stamps printed at Enschedé I did, indeed, detect some suggestions, especially in their simple frames and hollow lettering, of what the Michel catalogue calls Sägezahneffect
(saw-tooth effect, the mark of screen printing technique) but never so pronounced as with your Luxembourg S.G. 507.
Now your further comments explain everything. Of course, we have to be aware of the usual trade secrets.
Did Enschedé use a Goebel press for their line-engraved stamps?
Unfortunately, I have never seen images at sharp resolutions of such stamps as Netherlands S.G. C656-C660, C708-C712, 801, C826-C830, 1096 or Luxembourg S.G. C533-C534, 571, 637-639, 661, 696.
Line-engraved stamps actually fall into different categories depending on the type of press used in their production (and even on their printers' expertise).
Sometimes we compare the incomparable. See the differences among line-engraved stamps produced, say, in Austria, Britain, Czech Republic and France to name but a few of the various products each with assets of their own to their producer.
What compact beauty in its own right can be discovered in some exquisitely designed and ingeniously line-engraved stamps not losing anything of their delicate impact when magnified to the scale which they were conceived in despite the fact that the sure, sensitive hand of the master engraver engraved the die in the actual size of the stamp.
Just have a look at some recent Czech Republic line-engraved stamps printed lege artis
from flat plates on Waite & Saville diestamp print presses. They interpret, not merely reproduce, paintings and are shown on http://www.wnsstamps.post/en
Alfred Sisley "Canal Lock in Moret", 1882
Alfred Justitz "An Alley", 1924
Milos Jiranek "Sand Bargemen", 1910
Karel Spillar "Spring", 1912
Joza Uprka "Woman in Maize Field", 1910
Kamil Lhotak "Girl with Long Hair", 1951