The answer to your question lies in the Serial number. Below is some info that might help. Also, I think Plumber 101 is a Trane dude, he might be able to help better.
Trane used alpha codes in their serial numbers to determine year of manufacture. They started this in 1987 with the letter B and skipped the letters I, O, Q, U, Z
In 2002 they started their serial numbers with the year it was built.
The first letter of the serial number gives the year of manufacture as follows:
9=2009 8=2008 7=2007 6=2006 5=2005 4=2004
3=2003 2=2002 Z=2001 R=2000 P=1999 N=1998
M=97 L=96 K=95 J=94 H=93 G=92 F=91 E=90
D=89 C=88 B=87 S=86 Y=85 X=84 W=83
O, A=80(seventh digit)