A thread on 3rd gen G19 in classifieds made me think this may be useful. All data is from the excellent Glocktalk Serial Number Research Project compiled by dmobrien2001 (www.glocktalk.com, under general glocking/valuable info threads).
Format is 3 letter serial prefix (i.e. the ABC part of a ABC123US serial) - the manufacture date (= the test firing date on shell casing supplied with new glocks) - the generation - any other note such as non-US purchase, police dept use, LCI (loaded chamber indicator) etc.
This list should not be considered complete as they are constantly adding to it over glocktalk, but anything with a serial higher than the bottom of this list was probably made after 10/21/98, and anything lower won't be 3rd Gen.
CHY - G-20C - August 1997 - 3rd Gen. - First 3rd Gen. G-20C
CHY - G-20C - Unknown - 2nd Gen.
CKE - G-30 - July 1997 - 2.5 Gen.
CKF - G-20 - September 1997 - 2.5 Gen. - End of transition models, G-20
CKF - G-20 - September 1997 - 3rd Gen.
CKF - G-?? - January 1998
CKI - G-29 - Unknown - 2.5 Gen.
CKN - G-27 - July 1997 - 2.5 Gen.
CKT - G-29 - August 1997 - 2.5 Gen.
CKU - G-30 - July 1997
CKW - G-21 - September 1997 - 2.5 Gen.
CKY - G-22 - September 1997 - - factory night sights
CLA - G-23 - September 1997 - 2nd Gen.
CLB - G-26 - September 1997 - 2.5 Gen.
CLG - G-31 - October 1997 - 2nd Gen. - Early Prod./Rare 2nd Gen. Frame
CLM - G-22 - Unknown - 2nd Gen. - Philippines
CLN - G-28 - October 1997 - 3rd Gen.
CLW - G-27 - November 1997
CLX - G-29 - October 1997 - 3rd Gen.
CLY - G-30 - October 1997 - 2.5 Gen.
CME - G-17 - November 1997 - 3rd Gen.
CMF - G-19 - November 1997 - 2nd Gen.
CMK - G-22 - November 1997 - 2nd Gen.
CML - G-22 - December 1997
CMM - G-23 - November 1997 - 2nd Gen.
CMP - G-23 - December 1997 - 2nd Gen. - Sticker on case says LE/Military Only. Black 8lb connector. Purchased used.
CMT - G-30 - April 1998 - 3rd Gen.
CMY - G-19 - December 1997 - 2nd Gen.
CMZ - G-21 - December 1997
CNA - G-22 - Unknown - - LEO service weapon
CNK - G-24 - June 1999
CNM - G-17 - Unknown - 2nd Gen. - has Austrian proofs
CNS - G-20 - April 1998 - 3rd Gen. - First 3rd Gen. G-20
CNU - G-17 - January 1998
CNW - G-22 - January 1998 - 3rd Gen.
CPC - G-31 - January 1998
CPC - G-32 - January 1998
CPE - G-33 - February 1998 - 2.5 Gen.
CPH - G-19 - Unknown - 3rd Gen. - Austrian proof datecode EDT, no LCI
CPK - G-19 - Unknown - 3rd Gen. - Austrian proof, no LCI
CPL - G-19 - Unknown - 3rd Gen. - Austrian proof, no LCI
CPV - G-26 - February 1998 - 2.5 Gen. - smooth finger grooves
CPW - G-27 - March 1998 - 2.5 Gen. - no grooves for fingers
CPY - G-34 - April 1998 - 3rd Gen.
CRD - G-21 - March 1998
CRG - G-26 - March 1998 - 2.5 Gen.
CRK - G-31 - April 1998 - 3rd Gen.
CRL - G-32 - May 1998 - 3rd Gen.
CRP - G-22 - March 1995/September 1998/August 1999 - - three dates TG search. also is marked "Cedar Rapids Police"
CRT - G-19 - April 1998 - 3rd Gen.
CRX - G-23 - April 1998 - 3rd Gen.
CRZ - G-26 - April 1998 - 2.5 Gen. - smooth finger grips
CSA - G-27 - April 1998
CSB - G-27 - April 1998 - 2.5 Gen.
CSC - G-31 - April 1998 - 3rd Gen.
CSD - G-32 - May 1998 - 3rd Gen.
CSE - G-33 - April 1998 - 2.5 Gen.
CSN - G-19 - May 1998 - 3rd Gen.
CSR - G-21 - March 1998 - 3rd Gen.
CTB - G-34 - May 1998 - 3rd Gen.
CTF - G-23C - May 1998 - 3rd Gen. - (Rochester PD)
CTG - G-17 - June 1998 - 3rd Gen.
CTH - G-17 - June 1998 - 3rd Gen.
CTM - G-21 - June 1998 - 3rd Gen.
CTS - G-23 - June 1998 - 3rd Gen.
CUL – G-17 – July 1998 – 3rd Gen. – bought two, one fixed sights, other Trijicon NS
CUM - G-19 - July 1998 - 3rd Gen.
CUR - G-22 - July 1998
CUX - G-27 - July 1998
CUT - G-23 - July 1998 - 3rd Gen.
CVA - G-17 - Unknown - 3rd Gen. - Sweden
CVC - G-17 - September 1998
CVD - G-19 - August 1998
CVN - G-26 - September 1998 - 2.5 Gen.
CVX - G-17C - Unknown - 3rd Gen.
CVZ - G-23 - 1998 - - Germany, IDT Sep98
CWB - G-19 - September 1998 - 3rd Gen. - Philippines
CWD - G-19 - September 1998 - 3rd Gen.
CWH - G-?? - Unknown - 3rd Gen.
CWL - G-23 - September 1998 - 3rd Gen
CWS - G-35 - September 1998 - 3rd Gen.
CWT - G-17L - Unknown - 3rd Gen.
CWW - G-19 - October 1998 - 3rd Gen.
CWX - G-19 - November 1998 - 3rd Gen.
CWZ - G-22 - October 1998 - 3rd Gen.
CXB - G-22 - October 1998 - 2nd Gen.
CXD - G-23 - October 1998 - 3rd Gen.
CXE - G-27 - October 1998
CXG - G-27 - November 1998 - 3rd Gen.
CXH - G-30 - November 1998 - 2.5 Gen.
CXK - G-19C - November 1998 - 3rd Gen. - Purchased in Belgium
CXN - G-17 - November 1998 - 3rd Gen. - w/o extra locking block pin
CXP - G-19 - November 1998 - 3rd Gen.
CXT - G-22 - November 1998 - 3rd Gen.
CYC - G-30 - November 1998 - 3rd Gen.
Format is 3 letter serial prefix (i.e. the ABC part of a ABC123US serial) - the manufacture date (= the test firing date on shell casing supplied with new glocks) - the generation - any other note such as non-US purchase, police dept use, LCI (loaded chamber indicator) etc.
This list should not be considered complete as they are constantly adding to it over glocktalk, but anything with a serial higher than the bottom of this list was probably made after 10/21/98, and anything lower won't be 3rd Gen.
CHY - G-20C - August 1997 - 3rd Gen. - First 3rd Gen. G-20C
CHY - G-20C - Unknown - 2nd Gen.
CKE - G-30 - July 1997 - 2.5 Gen.
CKF - G-20 - September 1997 - 2.5 Gen. - End of transition models, G-20
CKF - G-20 - September 1997 - 3rd Gen.
CKF - G-?? - January 1998
CKI - G-29 - Unknown - 2.5 Gen.
CKN - G-27 - July 1997 - 2.5 Gen.
CKT - G-29 - August 1997 - 2.5 Gen.
CKU - G-30 - July 1997
CKW - G-21 - September 1997 - 2.5 Gen.
CKY - G-22 - September 1997 - - factory night sights
CLA - G-23 - September 1997 - 2nd Gen.
CLB - G-26 - September 1997 - 2.5 Gen.
CLG - G-31 - October 1997 - 2nd Gen. - Early Prod./Rare 2nd Gen. Frame
CLM - G-22 - Unknown - 2nd Gen. - Philippines
CLN - G-28 - October 1997 - 3rd Gen.
CLW - G-27 - November 1997
CLX - G-29 - October 1997 - 3rd Gen.
CLY - G-30 - October 1997 - 2.5 Gen.
CME - G-17 - November 1997 - 3rd Gen.
CMF - G-19 - November 1997 - 2nd Gen.
CMK - G-22 - November 1997 - 2nd Gen.
CML - G-22 - December 1997
CMM - G-23 - November 1997 - 2nd Gen.
CMP - G-23 - December 1997 - 2nd Gen. - Sticker on case says LE/Military Only. Black 8lb connector. Purchased used.
CMT - G-30 - April 1998 - 3rd Gen.
CMY - G-19 - December 1997 - 2nd Gen.
CMZ - G-21 - December 1997
CNA - G-22 - Unknown - - LEO service weapon
CNK - G-24 - June 1999
CNM - G-17 - Unknown - 2nd Gen. - has Austrian proofs
CNS - G-20 - April 1998 - 3rd Gen. - First 3rd Gen. G-20
CNU - G-17 - January 1998
CNW - G-22 - January 1998 - 3rd Gen.
CPC - G-31 - January 1998
CPC - G-32 - January 1998
CPE - G-33 - February 1998 - 2.5 Gen.
CPH - G-19 - Unknown - 3rd Gen. - Austrian proof datecode EDT, no LCI
CPK - G-19 - Unknown - 3rd Gen. - Austrian proof, no LCI
CPL - G-19 - Unknown - 3rd Gen. - Austrian proof, no LCI
CPV - G-26 - February 1998 - 2.5 Gen. - smooth finger grooves
CPW - G-27 - March 1998 - 2.5 Gen. - no grooves for fingers
CPY - G-34 - April 1998 - 3rd Gen.
CRD - G-21 - March 1998
CRG - G-26 - March 1998 - 2.5 Gen.
CRK - G-31 - April 1998 - 3rd Gen.
CRL - G-32 - May 1998 - 3rd Gen.
CRP - G-22 - March 1995/September 1998/August 1999 - - three dates TG search. also is marked "Cedar Rapids Police"
CRT - G-19 - April 1998 - 3rd Gen.
CRX - G-23 - April 1998 - 3rd Gen.
CRZ - G-26 - April 1998 - 2.5 Gen. - smooth finger grips
CSA - G-27 - April 1998
CSB - G-27 - April 1998 - 2.5 Gen.
CSC - G-31 - April 1998 - 3rd Gen.
CSD - G-32 - May 1998 - 3rd Gen.
CSE - G-33 - April 1998 - 2.5 Gen.
CSN - G-19 - May 1998 - 3rd Gen.
CSR - G-21 - March 1998 - 3rd Gen.
CTB - G-34 - May 1998 - 3rd Gen.
CTF - G-23C - May 1998 - 3rd Gen. - (Rochester PD)
CTG - G-17 - June 1998 - 3rd Gen.
CTH - G-17 - June 1998 - 3rd Gen.
CTM - G-21 - June 1998 - 3rd Gen.
CTS - G-23 - June 1998 - 3rd Gen.
CUL – G-17 – July 1998 – 3rd Gen. – bought two, one fixed sights, other Trijicon NS
CUM - G-19 - July 1998 - 3rd Gen.
CUR - G-22 - July 1998
CUX - G-27 - July 1998
CUT - G-23 - July 1998 - 3rd Gen.
CVA - G-17 - Unknown - 3rd Gen. - Sweden
CVC - G-17 - September 1998
CVD - G-19 - August 1998
CVN - G-26 - September 1998 - 2.5 Gen.
CVX - G-17C - Unknown - 3rd Gen.
CVZ - G-23 - 1998 - - Germany, IDT Sep98
CWB - G-19 - September 1998 - 3rd Gen. - Philippines
CWD - G-19 - September 1998 - 3rd Gen.
CWH - G-?? - Unknown - 3rd Gen.
CWL - G-23 - September 1998 - 3rd Gen
CWS - G-35 - September 1998 - 3rd Gen.
CWT - G-17L - Unknown - 3rd Gen.
CWW - G-19 - October 1998 - 3rd Gen.
CWX - G-19 - November 1998 - 3rd Gen.
CWZ - G-22 - October 1998 - 3rd Gen.
CXB - G-22 - October 1998 - 2nd Gen.
CXD - G-23 - October 1998 - 3rd Gen.
CXE - G-27 - October 1998
CXG - G-27 - November 1998 - 3rd Gen.
CXH - G-30 - November 1998 - 2.5 Gen.
CXK - G-19C - November 1998 - 3rd Gen. - Purchased in Belgium
CXN - G-17 - November 1998 - 3rd Gen. - w/o extra locking block pin
CXP - G-19 - November 1998 - 3rd Gen.
CXT - G-22 - November 1998 - 3rd Gen.
CYC - G-30 - November 1998 - 3rd Gen.