There is a reason why gun manufacturers get more money for Cerakoted guns. It is the best thing going. No it does not lessen a firearms value if done correct. It raises it. That means not from the DIY crowd. I have seen someone here talk about chipping. This must either be a shadetree gun...
The mark of Georgia with the P is to show this gun was a police issue gun made for Law Enforcement. Several were sold in the general market in Georgia.
You did because they are not considered firearms under ATFE, and do not require a form 4473 or background check. I do not remember the cut off year they are considered firearms, but muzzleloaders are exempt.