I purchased a used G21 yesterday for a really good price. According to the serial number research project, this pistol was born in may of 2000. Being 12 years old and having an unknown round count, are there any specific areas that I should inspect for parts that need replacing? I completely disassembled the slide to thoroughly clean it. It was covered in oil and the striker pin and channel were soaked. I didn't see anything abnormal in the slide or it's components. While cleaning the barrel, I happened to notice some discoloration within the chamber. This discoloration spans from roughly the 8 o'clock to 10 o'clock position within the chamber. I had assumed this to be normal, but wanted to ask and confirm to be certain. And here she is as I received her. Thanks in advance for any input.