This is a Case fillet knife, Model P203-6, that I believe dates to the 1960s:







The blade marking "CASE XX Chromium" means that it is chrome vanadium (carbon) steel with a chrome plating, a blade type Case used from the 1940s until the early 1980s, although they also used stainless steel (CASE XX STAINLESS) for some knives during that period.



P203-6 was discontinued in 1978 and replaced with 204-6, the same pattern but in stainless steel.

From a late 60s case catalog:



Same knife, different sheath, from the 1974 catalog:



(Info above is from internet posts by Steve Pfeiffer, author of Collecting Case Knives: Identification and Price Guide.)

I was actually looking to buy a boning knife when I found this one on eBay. (Recently I have gotten pretty good at deboning bone-in chicken thighs, which are a lot cheaper than buying deboned, plus I like the skin on. Also been deboning pork shoulders/butts. That's a weirdly shaped bone in there!)

I bought this knife thinking a fillet knife and a boning knife were the same thing — and the ad listed it as being both — but in subsequent research learned that they are not the same. Boning knives are more rigid. (This pleases me because now I get to go on the hunt for a proper boning knife.)

Very cool knife! For fun I'll show you one that I think is older:

Case XX Chromium Snack knife. The wooden case is worn through at the bottom from the many times this knife was used and then stored back in the wooden box:

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Come and take it!!

That does look like an old, well loved, knife, Yoda. Very nice!