Block mounts offer maximum protection against sticking, discolouration, dust and humidity. Stamps held securely in place by strong clamp-type seal. SF mounts are made from 100% polystyrene (free from softening agents, acids and stabilising chemicals). Antireflection coating prevents light interference. Special adhesive on reverse side of film (simply moisten and stick down!).
D = Doragard (closed top and bottom, open at back) d = double seal (closed top and bottom)