History:

When was the scratching developed and how has its manufacture changed over the years? As soon as I find out, I'll let you know. Latest snippet I picked up is that the West Midlands is such an intensely scratching-friendly region because there used to be numerous abbatoirs in the area.

The Fresher Foods Website has a section on the history of Pork Scratchings, available from the link at the side. 

There is also a Wikipedia entry for pork scratchings, which gives a brief description.