Thanks Buck!
Wikipedia is very helpful ...
http://en.wikipedia.org/wiki/Parkerizing
It's interesting that Glock is still using it ...
Glock Ges.m.b.H., an Austrian firearms manufacturer, uses a black Parkerizing process as a topcoat to a Tenifer process
to protect the slides of the pistols they manufacture. After applying the Tenifer process, a black Parkerized finish is applied
and the slide is protected even if the Parkerized finish were to wear off. Used this way, Parkerizing is thus becoming a protective
and decorative finishing technique that is used over other underlying improved techniques of metal protection.
Your additional info is much appreciated.
Tony