A further source of information on instruments dating from the eighteenth century is the Patent Office. Patents are a Worldwide form of "copywriting" a design and range from the useful to the bizarre and libraries / offices can be found in many countries. The object of a Patent is to protect the owner / inventor and to make his ideas known. One advantage of this is that the actual written part of the Patent is free of copyright and can be published.
Searching through the British Patent Office in London has revealed a number of patents for "Bagpipes and Like instruments" as they are categorized. These mostly cover "improvements" to the Great Highland Bagpipe and include the keywork systems, synthetic reeds and bags, tuning slides for chanters, child sized pipes.
In addition there are of course a vast number of Patents for all other varieties of musical instrument and some of these could also be applied to bagpipes.