Zanzibar. (Advice Of Receipt Mail). 1909. Registered, Advice of Receipt mail envelope addressed to London bearing SG 230, 15c ultramarine (pair) tied by Zanzibar date stamp 'My 1st 09' with boxed 'R/ Zanzibar' and oval 'A.R.' hand-stamp on face with London receiver '21st May'. Nice usage with Advice of Receipt hand-stamp.