Used American Heat Reclaiming Spiral Heat Exchanger, Type 1-V, 90 square feet heat transfer surface area. Shell is constructed of stainless steel; head is construction of carbon steel. Unit rated for 75 PSI at 275 degrees Fahrenheit. Inner pass measures 1/2 " x 24", outer pass measures 1/4" x 24". Shell thickness measures 0.109 inch. Includes 2" water inlet/outlet. New in 1975. Serial number 11069, National Board number 8279.