Apparently the mercury gilding was the process used on late 18th century swords with blue and gilt blades. They are amazingly beautiful works of art, but apparently the craftsmen had a short lifespan and by early 19th century, styles changed (or the artisans dies off) and the are collector items today.There is still a nice website to see, it is www.palmersarmoury.co.za Looks like they are still selling cannons, including this one and both the "Long Tom" and "Long Cecil". Incredible models, astronomically expensive of course. Also a section of articles, including one on how to do "mercurial gilding" - a process of applying gold finish by dissolving the gold in mercury. Never heard of that process before, and while it is basically a do-it-yourself guide, a good portion of it is devoted to warning how dangerous it is! Anyway, definitely worth having a look.