Leuchars were mostly known as a manufacturer and retailer for high end boxes and other fancy goods I think. Chess sets were only a very small part of what they sold.
Here is a good link http://www.antiquebox.org/leuchars/
British Chess Co. only seem to have made sets for about 15 years
http://www.fersht.com/The%20British%20Chess%20Company.htm
@chessspy1 Those are very interesting histories. It's sad though that none of the Jaques competitor survived (with the exception of Leuchars which is virtually Jaques). From what I can see today, those foregone competitors along with BCC have very good chess sets.