I brought back a Speedlock with Thuya wood inserts from Den Haag, the Netherlands back in '96. I believe Boker was using 440C at the time. My examples edge holds up well under mild to moderate cutting tasks. A quick pass or two on a crock stick, or fine diamond hone is all that is needed for edge maintenance. I hope that the now common top locks are NOT 420J-2. That would be a real shame. I find the general ergonomics of the Speedlock very nice.
"Blessed is the Lord my rock, who trains my hands for war, and my fingers for battle..." excerpted from Psalms 144.
The Boker Top Locks are normally supplied with the 420 Stainless steel and absolutely not 440C.
Only for the original big Top Lock and not the Top Lock II which is somewhat smaller/ pocket sized one can buy a separate blade made of 440C. You would have to exchange the original blade with the 440C one yourself but that can be done in a minut.
The reason they don't produce them with 440C blades is, and that's what Boker says themselves, "they produce so many Top Locks and also the automatic version "Speed Lock" that they couldn't produce enough 440C blades to fit". It seems that making a 440C blade is more complicated then making them from 420 Stainless Steel. Probably it's harder on the machinery.
You can buy a 440C blade but only for the big Speed Lock and Top Lock for about DM 40 that would be less then $20 in US currency from Boker.
If interested I will see what I can do for you guys & girls.