This is indeed puzzling! 62005RAZ SS is definitely a
W. R. Case & Sons pattern number.
(NB, everything that follows here is just speculation, fueled by my ignorance and curiosity.) Why the OP's knife is marked "Case Brothers Cutlery Co." I don't know. In addition, the designation of "
W.R. Case Case Brothers Cutlery Co." in the provided link seems odd to me as that is an amalgam of two different brands, and the pictured knife has a
W. R. Case & Sons tang stamp. From my research the 05 pattern (by W. R. Case & Sons) was introduced "before 1940," while
Case Brothers Cutlery Co. went out of business in 1915. Perhaps this is a historical marking used by
W. R. Case & Sons for some sort of commemorative event? Anyway, a very interesting history question and a very nice knife that perhaps might have some special history associated with it. I hope someone will come along and sort this out for us.
EDIT: I just re-read
Obsessed with Edges
post and this may well be the sort of unique tang stamp that he's talking about.
By the way, here's a short history that I found:
https://historicpath.com/place-themes-industry-cutlery/case-brothers
Oh, and yes, "XXX" would correspond to the seventh year of the decade for the past couple of decades of W. R. Case & Sons tang stamps. Although, as
5K Qs
points out, that's not the way we would normally expect them to be configured.
"Curiouser and curiouser!" cried Alice...