Henckels kitchen knives, what does the number mean?

[biogon]

I have a few low-end Henckels kitchen knives. (Nothing special, but they're better than the average household's "Never Needs Sharpening!" knives...)

There's a number on them -- what do they mean?

My paring and utility knives have "31320" on them.

My cleaver has "31134" on it.

I can't imagine this is a steel type -- there don't seem to be DIN numbers that match. It isn't a model designator (two have the same number). Is it a line indicator?

Also, does anyone know what steel Henckels uses for its blades? 420A?

Thanks!

-Jon