Mauritius 1863 QV De La Rue Reference Specimens, Rare

1863-72 QV wmk CC 1d, 2d, 4d, 9d & 5/- each handstamped SPECIMEN with type D5 (in black on the first three; in blue on the 9d & 5/-). Most probably from the De La Rue reference collection. Fair-F, couple imperfections, separated with scissors notwithstanding perforation! Samuel states that whilst perhaps between 1 and 6 examples of this stamp and handstamp combination may exist the D5 handstamp struck in either blue or red is most unusual and particularly elusive. The coloured impression may denote a special usage of the Specimen. A very rare group. Ex Samuel.