Claes Tilly was a religious man. This becomes evident by the text he placed at the top of the user manual: ‘this medicine works by the grace of the Almighty’
It was followed by a prayer:
“In Jesus Christ all the treasures of healing are concealed / thus the gifts of the flesh; all strengths of Healings / and all wise treatments of the cautious Master of Healing is from Him / through Him / and by Him : To Him the power and the glory for ever, Amen."
To protect himself against Haarlem Oil counterfeiters he used an encrypted text on all
historical user manuals. Above the encryption it says:
‘so that no one will be cheated he thus signed his leaflet'.
Over the centuries its significance was lost, until recently a member of the Haarlem archeological society deciphered the text. Using mirrors and lenses it read:
“Inv. Meester C.T." which meant: ‘Invented by Master Claes Tilly.
The purpose of the encryption was to enable the original manufacturer to expose
fraudulent use of the label and the product and consequently, in court, be able to prove counterfeiting. In addition each leaflet came with his signature in red ink.
The word Genuine (in Genuine Haarlem Oil) means that Claes Tilly was legally allowed to sell his product as the only real Haarlem Oil. This right was granted to him by the Haarlem Schout and Aldermen on October 9, 1723.