New Artisan Knife - Says "40 55" what does this mean?

[bagsjr]

Hi folks,

Merry Christmas. What does 40 55 mean? I'm guessing that it's some type of steel? I received this knife as a birthday present. Very happy with it but I need to learn.
"Greg's Knives" "Black Hills"

and "40 55" on the other side. A beautiful knife.

Thanks,
Bob.

 

[Locutus D'Borg]

Pic please.