Planning on acquiring a nice G19 with 3 pins soon. Just wondering if anyone knows (or has an educated guess) on when (approximate date) the first 3-pin G19's appeared. I believe they must have been gen 3, not gen 2.5. Thanks in advance! 
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Only on the very few that are Austrian-proofed.don't know if state-sides produced glocks have the same stamping?!
What we understand to be the proofmarks are visible on both the barrel and the slide, but we only receive proofmarked guns when they have a shortage of US guns and presumably a surplus of proofed guns. Since the date code only appears on the proofed guns, I presume it is the date of the proof firing.i see, so the three letters are a kind of austrian proofmarks only.
taggeddon't know how it is with glocks produced in the states, but with all glocks produced in austria, you don't need the serial number to get the "date of birth" of your glock.
glock austria stamps 3 letters on the rearward part of the barrel, f.e. GOM means (according to the list below) july 2005, G for july, O for 0 and M for 5, so july 05.
the first of the three letters stands for the month of production
E*-*January
L*-*February
N*-*March
B*-*April
S*-*May
Z*-*June
G*-*July
P*-*August
I*-*September
C*-*Oktober
V*-*November
A*-*December
the next two of the three letters stand for the year of production
O*-*0
W*-*1
K*-*2
R*-*3
F*-*4
M*-*5
H*-*6
Y*-*7
T*-*8
D*-*9
don't know if state-sides produced glocks have the same stamping?!