Grey Seal a "superhero" (although recruited into fighting the mob) Seems more like the gentleman thief type , more in the vein of Fantômas, created 1911, who also had a movie in 1913. At best these might be proto-superheroes.
Superhero fiction is just a sub-genre of all Heroic fiction, just people want to move and draw arbitrary lines all over the place to qualify the "first" Superheroes.
Either with nuances of character or identity, specific skills abilities weather they are "super" or not, how "real" their world is, was or has remained, whether the costume or mask qualifies as a costume or not,, etc...LOL.
Most would correctly classify it as beginning around the popularity and trend of Superman and the American comic book explosion and everything it inspired. Others want to move it back, to the things that influence Superman & Batman, the comic-strip characters Phantom, Mandrake, Flash Gordon, Dick Tracy, ...etc, to the pulp-magazines and radio heroes, Tarzan, The Shadow, Zorro, John Carter, Doc Savage, Green Hornet, etc. , to gothic and victorian era heroes the Pimpernel or Monte-Cristo who disguises and reinvents himself to seek revenge on the corrupt and those who wronged him. To the middle ages and knights and fables, even further all the way back to heroic epics and classics , Beowulf, Hercules, Gilgamesh and the oldest recorded stories. LOL!
Which defeats the whole purpose of the classification to begin with.
It just becomes arbitrary and meaningless.