Yes, assume it is original. A-S boilers became part of Burnham somewhere in there. It has a steady state efficiency around 80% because of the way they rated input & output. But the figure that relates to the gas bill, annual efficiency is probably 60% or less. That means that during start up, shut down & off cycle, it loses so much heat that the 80% during run really means that 60% of the gas you pay for heats the house, 40% goes up the chimney. And 525K input reall spins the old gas meter