1906 NATAL TRAVELLING POST OFFICE: KEVII 4d Transvaal Registered Letter Envelope uprated 2d from Standerton to Durban. On reverse the very scarce T.P.O/NATAL double circle cds (Hart Type W3) dated 27 DEC, recording the processing of the mail on rail between Elandsfontein & Charlestown before the Natal border was reached. A little soiled but still most desirable.