I would be careful with the langet attribution, as many past the 1820s were marked and cutlered on both sides of the channel. The Mowbray book still the gold standard for the early swords but there are some tdbits in Hartzler's Lattimer Collection book. Flayderman and the younger Mowbray publishing the Medicus Collection offers a very comprehensive (while sparse reading) flash card deck.
The early use of eagles with langets actually goes (in part} to Le Page and others in France.
Eagle types almost infinite. Below an older link to my eagle mania. Some misplaced on purpose, others simply misfiled, a general image dump of mine up to a few years ago. My current drive still updated almost daily, so this shared folder just a start
https://drive.google.com/folderview?...mM&usp=sharing
Just a for instance, one will find Dyer types in both the Salter folder and a separate subfolder under another category. Similarly, I have Bates and Bolton together. I may never publish more than these simple posts but I pretty much still live and breath eagle pommels. I don't think I'll ever have all the knowledge.
With the variety so, so diverse, it is much easier to discuss a paticular variety than speaking in broad terms.
Cheers
GC