The Twenty-five Pence stamp with this issue is unique amongst Discworld Stamps as it carries a advertisement by means of an underprint - in this case a company logo - printed on the gummed side of the stamp. The prototype is the 1893 definitives of New Zealand, commonly referred as ‘Adsons’, but other similar and earlier stamps exist.
Joseph Camels is the Mayor of Sto Lat, local bigwig, and proprietor of his parasol emporium. The stamps are in a sheet of 20 with each stamp underprinted. There is slight variation regarding the verticality of each print and one has the underprint inverted - count this as a Sport if you like. The sheets were available as a limited edition of 200 and only available to subscribers to the Stanley Howler Stamp Journal (though the security attached to ensure that was hardly secure). A single stamp, without the underprint, was a free gift with that same august publication.

Below are a pair of test print sheets for this stamp. The first shows an (probably early) colour choice of blue; too close to the Two Pence stamp in reality. A single stamp image from the sheet shows that the border to the illustration of the town is in a contrasting colour, which was retained in principle for the Two Pence, but not used on the Five Pence. The sheet is printed on ungummed thick A4 paper.

The second sheet is printed on thinner A4 cream paper and has the stamps in the final colour and set in the final sheet design. The adverts are printed on the reverse.