Boker does use 440c on many knives, but "high carbon stainless steel" can be any steel with about .50% carbon and up so 420hc,440a, aus8,8/9cr1Xmov and even that 1.4XXX stuff can be described as so.
I have a Hyper in 440c(china). the knife been in my edc rotation since 2009 great knife slim, lightweight, blade performs bigger that its size with that belly and recurve. Whether its a true 440c or chinese equivalent in my experience it performs a tad better than many aus8 excluding whatever voodoo coldsteel does with theirs . Sharpening wise even with recurve i can easily get the knife sharp without any resistance difficultly of say higher end stainless like 154cm or s30v
