This is a 1918  1d Red stamp + right margin, perforated OS for Official Service,  from the 1918-24 issue of the King George V stamps with Large Multiple Crown over A watermark, with Comb 14.25 x 14 perforations. It is also a variety stamp, Plate 3 stamp V30, BW74(3)d - 'damaged lower right frame'. CV of ~$600-700.

Stamp is in very fine condition, with bright, sharp colour, great perforations and reasonably centred (towards the left). See first scan. 

The variety is shown in more detail in the second scan.

The stamp and margin is in mint, unhinged condition.  

Reverse side of the stamp is as per the third scan. Clean, white and smooth gum, with a bit of aniline colour penetration. A toned perf tip at top.