India 1861 cover from Calcutta to England with 1856-64 2a yellow-buff

1861 (DE 9) large part cover (missing side flaps) from Calcutta to England, endorsed 'Via Marseilles', franked at 6a by 1856-64 2a yellow-buff and 4a black, tied by mostly very fine strike of 'CALCUTTA / 1' duplex and horizontal pen strokes, with boxed 'INDIA PAID' h/s in red at lower left and London arrival (JA 13 62) backstamp. A neat and appealing usage, the sender clearly with much to say as the envelope has been opened out to allow for additional writing space !