Quink Concentrate

At just two inches (5 cm) high, this is one of Parker's smallest Quink ink bottles. The instructions on the side of the box state:

Pour the contents of the phial into a 4-OZ. bottle and fill with CLEAN COLD WATER.
In doing this BE SURE TO RINSE out the phial several times to make certain that ALL the content is used.

Quink Concentrate was a WW2-era product, marketed in the UK. The ad below explains more, noting that "the bottle shortage is greater than ever". The need to economize on shipping was a major concern during wartime; another response to this need was "V-mail", in which letters were copied to microfilm and re-printed at the letter's destination. Unused WW2-era V-mail ink is still commonly found in the USA.