b'31183183P 1920-21 FOUR PENCE COLOUR TRIALS: 4d colour trial in brown-purple (brown) endorsed on the reverse B in red, Cat $15,000. .$10,00012,500184184P 1920-21 FOUR PENCE COLOUR TRIALS: 4d colour trial in warm brown-purple (bright brown) endorsed on the reverse C in red, Cat $15,000. $10,00012,500185185P 1920-21 FOUR PENCE COLOUR TRIALS: 4d colour trial in warm red-purple (deep reddish purple) endorsed on the reverse N in red, exceptional centring, Cat $15,000. $10,00012,500'