You have been lied to someone put a Parker Brothers buttplate on a non Parker Brothers gun

Well this is the kind of info I'm looking for, so is Parker at one time Parker Brother or are the different companies, does any of the numbers of the pictures help identify the shotgun?

Your gun was made in Belgium not anything to do with Parker Bros. in the USA. Sorry

For your own safety, and that of those around you, please do not shoot this gun until the barrels have been checked by a qualified gunsmith and deemed safe to shoot. Barrel wall thickness and the severity of any pitting in the barrels are the two most important factors in determining this.
Even if safe to shoot make sure to use 2 1/2 inch low pressure loads such as those made by RST since your gun probably started life with 2 5/8 in. chambers.