The expression I don't understand
This is the excerpt of the book "Shawshank Redemption"

There was a trusty, name of Kendricks, who was into me for some pretty heavy money back in the fifties, and it was four years before he got it all paid off. Most of the interest he paid me was information - in my line of work, you're dead if you can't find ways of keeping your ear to the ground. This Kendricks, for instance, had access to records I was never going to see running a stamper down in the goddam plate-shop.

What does "running a stamper down in the goddam plate-shop" mean?

Question

The expression I don't understand
This is the excerpt of the book "Shawshank Redemption"

There was a trusty, name of Kendricks, who was into me for some pretty heavy money back in the fifties, and it was four years before he got it all paid off. Most of the interest he paid me was information - in my line of work, you're dead if you can't find ways of keeping your ear to the ground. This Kendricks, for instance, had access to records I was never going to see running a stamper down in the goddam plate-shop.

What does "running a stamper down in the goddam plate-shop" mean?

Answer

A common job in a prison, where the character is now, is, or at least used to, making car license/number plates in a prison factory. The machine that made them in a "stamper." The factory is the "plate shop"

So he was making license plates in this shop.

Answer

I'm not positive but I think it is to do with his job, it sounds like he worked making number plates for cars?