Very cool, thanks for the insight. Are you saying the characters themselves are upside down or the order of the characters is reversed from the standard? Also, is there any indication as to the age of the blade from the signatures?
In any case, here's what little I know on the blade. Bought it yesterday at a local antique shop and was told it was a very recent estate sale purchase and that they didn't know much else about it.
I have a couple decent machine made "replica" nihonto so thats really all I have to compare it too. Interestingly, it feels much heavier (but more balanced) than my machine made knock-off blade although they are almost identically sized. I don't know if it matters but I also noticed the hole in the tang looks like it was reamed or chiseled out as opposed to drilled clean.
Here are a few more pictures, thanks again for taking the time to reply with any thoughts.