acidic paper t.57:vyp.1(1925),t.58:vyp.2(1926)-t.59:vyp.1(1927),t.60:vyp.2(1928)-t.62:vyp.4(1930) acidic paper pH pen test brittle covers t.62:vyp.1(1930) brittle covers double fold test--breakage on second fold stained covers t.60:vyp.2(1928) stained pages t.60:vyp.2(1928)