If you look closely at the photo of the mei, that one character is the only one completely obscured. It alone has much more damage to it than the others. Damage which looks to be where someone used a chisel or punch to defile it.
It is not uncommon, and was kind of the poor mans way of removing a mei. The correct, but much more expensive way is to have a polisher remove it and professionally replace the file marks and patination.
Perhaps it is my destiny to have old blades with signatures removed, as evidenced by my partial Rohm.
I'll send you an email regarding the polishing, etc. we discussed previously.