waterlow & sons produced many small sheetlets of sample stamps in the same design as genuine stamps produced for their customers, but with the colours changed and overprinted diagonally "waterlow & sons ltd. specimen". the stamps in these sheetlets were also punched with a small hole in the corner to prevent their postal or revenue use and the sheetlets were displayed at the 1910 brussels exhibition. clive akerman comments in "the presentation of revenue stamps: taxes and duties in south america", that the stamps were produced from obsolete dies.