I would like to take a minute to recommend the (paid) services and publications of Markus Sesko to any Nihonto enthusiast.
Markus is not only a very friendly person but one of the foremost authorities on translating Nihonto related Japanese works into English.
His books are a great asset for any collector and highly recommended. If you do not own them yet, go for them!
Investing in excellent books first is a much smarter investment then buying a sword. Having his books will pay off in many ways and are a must have for your library.
Furthermore Markus offers translation services at very reasonable and thus affordable cost as well as appraisals.
If you have some though Sayagaki, Signature or Origami he is the man to ask. Markus can also give you an appraisal to count own at a modest price.
I can recommend him without hesitation and admire his oppinion.