Brake Caliper, Is this normal?

This is my first bike, and first time tearing down a caliper. When I took the piston cylinders out, I noticed on one side there seems to be a pattern in the metal. At first I thought it was a factory thing, but it's worn down on one side so I am thinking maybe the pressure from the brake fluid did this. However, when you look on the bottom of the piston cylinder there is no such pattern. I am mainly wanting to know if they are still safe/ok to use. I am upgrading to a bigger brake rotor, and bought this caliper used and wanted to change all the seals when I discovered this. Bike: WR250R, Caliper from WR250X
TLDR;
Is this safe/ok to use?

CALIPER UNDER PISTON CYLINDER


BACK OF PISTON CYLINDER




???

THANKS,

A fluid cannot create patterned indentations on a metal surface, but yes, the caliper is perfectly safe to use; clean those pistons thoroughly with soapy water and a toothbrush, and after you install them make sure they both move in synchrony when you apply the brake.

BTW, if you plan on riding off-road, the WRX brakes are not a good idea.