Why is this valuable? what is it worth?

Blotters – technical developments in the production of paper and writing instruments

Blotting paper was first used in Britain in the 15^th century. It became widely used in the 19^th century. This example is a result of a technological development that allowed one side of the absorbent paper to be coated and printed in full colour. The blotter’s demise came with the development of the ballpoint pen.

Looking back at the blotters now they are full of marketing pitches, like this one that we all know about now – securing bank customers from childhood.  Valued by Rick Milne at $10.