Examining the quality and quantity of engraving on European guild guns has some value. Although they could, most makers didn't put a lot of high quality engraving on a poorly made gun.
Now if someone is trying to decide which Parker DH 12 gauge to buy by divining the quality of one to another based on the quality of the engraving on each, no useful information there.
I like English and American guns. I boast that I have a tween-the-wars London sidelock 20 bore. And also brag on my high grade Parker 20 gauge. The fit, finish, and engraving are all superior on the London sidelock. The Parker is still a beautiful, quality gun,
The American guns do run a little heavier, gauge to gauge, than the English and the European guns. But the standard cartridges do too. Standard load for a US 28 ga is 3/4oz, UK 5/8oz. US 20 ga is 7/8oz, UK 20 is 3/4oz. US 16 ga is 1oz, UK 16 is 7/8oz.
12 gauge 1-1/8oz compared to 1-1/16.
I am a big fan of the Fox XE grade guns. The engraving on them, though not up to the standards of a higher grade Scott or Beesley or Imman. Meffert, compare very favorably in my eye to those guns. The pattern and engraving style give the Fox XEs a needed boost I think.
I defer to your expertise on the internals of the different categories.
It pleases me that you find the Fox mechanics strong and well designed. Again, I just don't know much about the internals. I really like the Fox guns. And the Parkers. And the Ithacas.
I think the German pre-WWII guns have to be the biggest bargain on the planet in terms of quality per dollar.
Best,
Mike