working backward

OK, i had a nat. gas heating unit this past weekend - i have the serial no#, etc but could fine no manufacturer info. can someone provide some assistance?
i was told it was put in 1997…

any help is appreciated.

model - PMKM-LD12N080G
serial - EGEM259998

Made in York, PA? Parent Co. is York might be a York or a Winchester or a Coleman residential

The third letter of the serial number would indicate that it was manufactured in 1996, so a 1997 installation would be normal.