SEYCHELLES SG128/a 1935 Silver Jubilee 6c Variety Extra flagstaff

1935 Silver Jubilee 6c ultramarine and grey-black lower left corner block of 4 from vignette plate 1 showing variety Extra flagstaff on R9/1 fine lightly mounted mint (fractionally yellowish gum as usual but very fresh appearance). A very scarce positional block. Total printing only 1798 sheets from 10 vignette plates with this variety not yet present in the large first printing of 935 sheets. Purchased from Stanley Gibbons (still on their card)