Hi Tony, Parkerizing, bonderizing, phosphating, or phosphatizing is a method of protecting a steel surface from corrosion and increasing its resistance to wear through the application of a chemical phosphate conversion coating.

Parkerizing is a chemically bonded non reflective phosphate coating that resists the elements much better than standard blueing. It has been widely used on military firearms to increase durability. (Example of a standard blued P32 is ) https://gearfireimages.s3.amazonaws.com/imagedb/image55814-181424cafe71196e1aec6b9dc328621d.jpg - (Example of a parkerized P32 is ) sportsmanswarehouse.com/img/products/original/keltec_p3at_pistol_1456723_3.jpg

parkerized is a duller more rugged finish than traditional blueing it was used on a lot of Military firearms