G'day, ladies and gents. Am trying to identify age and answer a few basic questions about an older, gas-fired hot water boiler. Equipment is installed in a large (6,500 - 7,000 s.f.) home built in 1964. Nameplate says "American Standard", series is 1B-Z1, and serial or boiler number is G-408. Plate states input BTU is 525,000, and output BTU is 420,000. I can't seem to find any very specific information on the boiler age using typical web searches, and have to assume that the equipment is probably original to the home. My friend (the home owner) says the unit still works, but is trying to figure-out whether he should be budgeting for an eventual replacement. I suggested to him that if the equipment IS original (i.e. almost 50 years), he should probably be budgeting for a new boiler. Can anyone verify that this might be original equipment based on the plate numbers? And if so...is 50 years a good, general life expectancy for a cast iron boiler of this type? Finally, can I assume, based-upon the BTU information, that this was an 80% efficiency unit? Seems strange for a 1964 model, if that's what it is?? Thanks for your time and opinion(s).