If you are just beginning to become interested in this, I recommend the following book from John Yumoto. Its quite old and basic, but still useful I think.
For something a bit more in-depth, I recommend:
For something a bit more immediately accessible I suggest joining the Nihonto Message Board. The members there are probably the brightest non-native Japanese sword enthusiasts around.
A matching signature is a good thing, but the sword enthusiasts will want to make sure that the actual sword resembles what a Zenshiro Ippo sword ought to look like. But I would also say that while we see a lot of crap pieces getting posted to the forum, yours doesn't give me that knee-jerk "junk" reaction. Would like to see more - or if there are any documents that came with the sword it would be interesting to see those too.