It is a nice knife.

I have bought and sold a number over the years.

They eventually moved away from the lesser steels to better ones. I don't know what they were using in 1997 when your knife was made, but they can tell you.

They can also probably tell you what the 31 indicates.

According to info at this website your 1997 knife probably has a BG-42 blade. https://en.wikipedia.org/wiki/Sebenza

If it holds a good edge, then you should get good use from it.

Congratulations.

Larry