Lamp black and linseed oil leave letters with a particular flow when printed on paper. But then, paper varies a lot in its absorbing properties: this one absorbs very little, it appears a bit waxy- the ink just stays neatly where the stamp placed it.
The gent who sold it to me at the antiques book shop in Camden Town, said it dated from around 1750. He didn't have any blank paper, but this one, featuring a tall and very narrow church tower has space for seven labels.
A coulple of days after I published this post, my colleague Andrew Ryan posted his method of printing lables on his facebook wall. There was quite a bit to learn from, and this is why we made some more, this time using a roller to spread the ink on the marble and a vice for printing.