One used De Dietrich Glass Lined Filter. Top National Board# 7567, serial# 36682, built 2003, glass 3009, rated 100 psi & Full Vacuum at 500 degrees F. Section 1 National Board# 4281, serial# 33608, built 1987, internal rated 100 psi & Full Vacuum at 500 degrees F, jacket rated 90 psi at 500 degrees F, glass 3008, section 2 same.