'High carbon stainless' is essentially anything with 0.5% or more carbon (the minimum to be called 'high carbon' steel of any kind, whether stainless or not), and ~12% chromium content (the minimum to be called 'stainless'). By that definition, it's not going to take a natural 'patina' (by oxidation) like a non-stainless 'carbon' steel will, though it can be etched or stained to emulate a somewhat greyer 'patina-ish' look. When stainless steel 'oxidizes', it's not a dark iron oxide that forms, but a very thin & essentially invisible layer of chromium oxide, which reacts more immediately to the presence of oxygen, and therefore prevents the iron in the underlying steel from oxidizing. That is how it's 'stainless' (which means it 'stains LESS', but still won't quite be rust-proof).
The minimum 0.5% carbon requirement (give or take ~0.5%) is what allows most decent cutlery steels to be hardened by heat treat, which then allows the steel to take and hold a relatively sharp, thin and durable edge. So, almost any reputable cutlery designed to take and hold a sharp edge will likely meet that 'high carbon' definition, whether stainless or not. The 'high carbon stainless' moniker could therefore be applied to almost any decent stainless steel used for sharpenable knives; that would mean essentially everything from 420HC (which was created and named to meet that 'High Carbon' definition, as other variants of '420' had less carbon) and up. Other 'cutlery', like stainless flatware (knives, forks, spoons) will usually contain lower amounts of carbon (maybe much lower), which then limits or prevents their ability to be hardened for edge-holding.
Chances are, the 'high carbon stainless' blades in Boker's traditional knives will very closely approximate that minimum 'high carbon stainless' standard, in something like 420HC or equivalents from Germany/Europe, maybe China, depending on where the steel & knife materials were sourced. The 'high carbon stainless' labelling is sort of a catch-all for the most basic stainless blades. Higher-alloy specialty steels will usually be specifically identified (440C, 12C27, etc), as that's usually a selling point in itself.
David
