134851 1951 1D LIGHT ULTRAMARINE (SG504) BLOCK OF 40 WITH 'KEYHOLE FLAW' (SPEC Q6d).

1951 1D LIGHT ULTRAMARINE (SG504) BLOCK OF 40 WITH 'KEYHOLE FLAW' (SPEC Q6d). A superb unmounted o.g. upper right corner marginal block of 40 1951 1d light ultramarine (SG504) with the very rare variety 'KEYHOLE FLAW' on stamp 6/12 (Spec Q6d). A very rare positional block with sheet number '935160' and the first example we have handled for many many years. (Ref 134851).