TANZANIA SGO37/a Official 1970 50c on glazed paper Pair inc Error OFFCIAL

Official. 1970-73 50c on glazed paper type O4 local opt vertical pair upper stamp error OFFCIAL (R7/6) lightly cancelled by part cds. One short perf but scarce in this se-tenant form. (cat ??104+). Purchased from Stanley Gibbons (still on their card)