What's the more generic name for the inletted Winchester super grade sling swivels? I want to say Whelen or maybe Howell style but not sure, seems the only terminology I'm finding is "inletted sling swivels".

These:

Cooper refers to them as - inlayed sling swivels

drover

Sunny Hill refers to them as (Winchester "Super Grade" Sling Swivel Set - Mild Steel)

I like them, very classy.