I noticed this small cardboard box being used by my mom, an octogenarian, to preserve a valuable memory of hers from a long time ago. The box is of W & R Balston Ltd’s Whatman Filter Paper No.1, Made in England.
Searching online I learned that:
- the design of the box was from the 1950s or earlier;
- the filter papers were mostly used in chemical processes (maybe we used it when my family #LIFCOBOOKS owned a book printing press in North Arcot District in the 1950s);
- there are many grades of the filter paper each with a unique number to identify the Particle retention capabilities and the thickness.