Boilers are also a fun thing to decipher manufacture date. Most do not code their year of make in their serial numbers, although some of this info is within the unit. Of course, we are not taking the boiler apart, so we are not easily able to find this. Safe bet is to write down the serial number and brand and call the manufacturer. I routinely have to do this with Burnham, New Yorker, etc. Furnaces are a heck of a lot easier once you know the various manufacturer keys after years of experience.