What do the first 4 letter stand for? Are they company name that made the tool or something else? ( From history )
Here's a clearer image (taken from http://iantiqueonline.ning.com/group/whadjafind/forum/topics/japanese-kanji-katana-samurai-sword-i-d-help?)



The text is verbatim:




  張武傑 (seal of a person called 張武傑). Maybe this is supposed to suggest that 張武傑 was involved in the manufacturing.


联合刀具


  The name of a company called 联合 cutting tools. 联合 should not be translated into union here, but treated as a proper noun. It might be in imitation of an American company originally called Union Cutlery Co., now called Ka-Bar Knives., Inc; this company's Chinese name is frequently rendered as 联合刀具.


特殊鋼


  Special steel. According to baidu, this is a non-standardised grade of steel, so it doesn't really mean anything.




In terms of orthography,「联」is normally only used in Mainland China, while「鋼」is normally not used in Mainland China. The structure of「联」, simplified from「聯」, is exactly analogous to the simplification of「關」to「関」.「関」is now normally only used in Japan.