What does it say on the carved seal blade?

The Japanese character mark of backside blade means blade material. 

As we can't tell the difference non mark, we attached it making process.    

 

ibuki white 2 steel, AUS-8,ZA-18, HAP40 non edged models: non mark

ibuki blue 2 steel model: 青鋼　

ibuki Aogami super model: 青紙スーパー

ibuki silver 3 steel model: 銀紙3号

ibuki vg-10 model: V金ゴールド

Daisuke model: 大祐, black smith name
Muneishi model: 宗石, black smith name

limited model：息吹, our bland name is ibuki

another words: 鍛造, forged by hand work