good idea using the magnifying glass
I've checked the information I have gathered so far and must admit that I've never came across that kind of marking.
Quite interesting is the fact that the marking is on the "shoulder" of the blade and not on the side, because normally blades were marked there.
Judging by the crown, I would guess the blade was forged in England perhaps first half of the 19th century. The strange grip and the observations made by broadaxe seem to indicate that the weapon was made up at a later point in time using (at least) an older blade (perhaps even the guard).
Do you mind posting pictures of the pommel? This might show if the blade is threaded (which can be another indicator for the forging time).
William