Hi, I'm no knife expert, but I'll try and translate the characters for you.
first on the left:-
at the top, the two kanji side by side: 登録
とうろく (touroku): registration, register, entry, record.
then below that: 堺
さかい (sakai):
Sakai, Osaka
文字
もじ (moji): characters
平作
へいさく (heisaku): normal (average) crop.
in the middle:-
源: みなもと (minamoto): source, origin
菊文: きくふみ (Kikufumi): a given name
字: あざ (aza): section of village
Kikufumi was a little difficult, but I think it's just saying that the knife came from "Kikufumi's" section of the village.
on the right:-
極上
ごくじょう (gokujou): first-rate, finest quality, the best.
I hope that helps.