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.
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.