Saw this on ebay and it made me smile
This auction is for a box of Ilford Multigrade 8.9 cm x 8.9 cm darkroom filters for increasing the contrast levels in your black and white prints.
There are 10 filters from 00 to 5 including half filters (e.g 2 1/2)...
(However 4 is missing but this can be replaced by using 3 and 1 at the same time). Unquote
I wonder if he ever mastered the contrast thing!