One more tidbit of info which I didn't know but just tracked down concerns the W (broad arrow) D mark found on much Crown equipment. This mark apparently dates from 1855. That's when the WD, or War Department, superceded the Board of Ordnance. You probably already know that but if I write it down like this I tend to remember it later.

You can see the various marks found on some British edged weapons at the site below, and how they say the WD dates from 1855.