J6ac, J6a (D9a, D9) 1929 18¢ black on salmon Postage Due typeset, rouletted 10, VARIETY - "cent.s" for "cents.", only occurred once per sheet of 10 (row 4, pos 1) of the initial printing, top stamp in vertical pair with normal, unwmkd, rare and undercatalogued, light "Zanzibar" double-ring cds.
