The reason why you recognize the last kanji, saku - 作, is because it just means production or manufactured. Most knife brands put that at the end of their names. Kind of like saying osaka joe manufacturing.
Anyways to get on to the other kanji. It can be read one of two ways.
長俊作 Nagatoshi-saku or Choshun-saku.
More likely Nagatoshi as the other one is worded strangely.