Slant/Fin gas fired boiler ser#1152326.
this is all I could find out about dating a Slant Fin gas boiler, however it does not see to fit your case. Are you sure the ser# you quoted is correct.
**Slant Fin – Present day **
Serial Number format: G0049257
(This serial number was transcribed from an actual unit during a home inspection).
Using the second thru fifth digits G0049257 you will find the year and week of manufacture. The first set of digits is the year and second set of digits are the week. This unit was manufactured in the 49th week of 2000.
Year of manufacture: G0049257
Week of manufacture: GSD0049257