As more girls advertised their services the cards became larger - A7 or less frequently one third of A5 - and more distinctive. Girls developed their own recognisable style. Specialised services were offered and a visual and written vocabulary began to evolve to reflect each specialism. Cards offering schoolgirl services or Le Vice Anglais had a Victorian feel and accordingly used nineteenth-century typefaces; domination cards used stern words set in Gothic letters; cards proffering massage needed a luxurious and whimsical script.Link
These mid-period cards were predominantly typographic and were supported by roughly drawn, but often delightful, line illustrations. They managed to maintain both a sense of mystery and a sense of humour. Eventually the ISO standards made themselves felt even in the vice industry, and by January 1994 nearly all the cards had been enlarged to A6 postcard size. Four-colour started to be seen on the cards during the summer of 1997, and by the summer of 1998, four-colour, and ‘proper' typesetting was the norm.
Today's cards depend upon full-page, sometimes explicit, glossy, photographic images to put across their sales pitch. The images are downloaded from the Internet and are never of the person offering the services, although they are often advertised as ‘genuine'! The charm and allure apparent in the early cards has gone from the modern cards, individuality and originality has been lost...
The cards are placed in the boxes on behalf of the girls by people known as ‘carders' who are frequently students or unemployed. It is a highly lucrative trade and the carders can earn an average of £30 for 100 or £200 per day for between 600 and 700 cards placed. The girls pay for the carders out of their own wages, and with thirteen million of them placed annually, the wages of sin are in the region of £4 million.
(via Foe Romeo)