Here is another Gun Digest advert - from 1992. The G22 pictured is serial number NP000 (I assume US as well, but obviously I cannot verify). Take note that the Glock, Inc. logo has changed from the 1990 advert.
USMCR 1997 - 2004
PAARNG 2011 - Present
Founder - Glock Collectors Club PA Glocker #39
Looking for G22 PE389US
Multiple Armorer Certifications