One more note about the letters...
The four letters in "Mous" are centered directly above the four letters "Hole". True, the "S" is worn more than the other letters, but if an "E" followed that "S" and is completely worn away, it would have made the word strangly off center.
Also- the larger, partial letter below "Mous Hole" that looks like the top of a "C", "S", or G" shows no sign whatsoever of having a bottom half, nor any other letters aroud it. Perhaps it is a nick and not a letter? There are a lot of nicks in the side as if someone used it as a chopping block. One cuts right into the mystery letter. Even very close examination shows no sign of a botton half of the letter, if it is one. I assumed it was a letter because it is a curved mark with a little nub on the end like one would see in the top half of a "C".
I know the early Mouse Hole anvils had only the simple name logo. But this one has a step, which those early oes (I believe) did not.
ALSO- I have done some VERY careful examination and can't find ANY other letters or parts of letters on the side of the anvil. Since the letters "Mous Hole" are so deeply stamped, one would expect at least a couple of the letters from any other original markings to remain!