Old files can make wonderful knives. Many of these tools were made from proprietary alloys that would today be considered boutique specialty knife alloys like Japanese White Paper steel. If executed properly the old file steel has great edge retention while being relatively easy to sharpen compared to high end stainless alloys. The other difference is the heat treat can be manipulated to make the blade stronger and more resilient. I personally also like the look and the story that goes along with the blade.

Here’s an example. This blade was made from a circa 1900 G&H Black Diamond mill file. You’ll notice, stamped on the file is “Best Cast Steel”. This is really what we call Crucible Steel now. Crucible steel was an expensive process where they’d make a pure iron billet, melt it down and add a controlled amount of carbon by way of cast iron and cast billets.

Around 1907 this company was bought out by Nicholson File Works and became the Black Diamond brand. In 1970 Nicolson which owned a lot of regional brands consolodated and discontinued most of those but due to the overwhelming popularity of the Black Diamond brand recognition that name is still used today. Before 1970 the files just had “Black Diamond” but after 1971 they will appear with both “Black Diamond” and “Nicholson” names.

Note the square shoulders at the tang and "Best Cast Steel" stamp.  While there were a few files like Delta that carried that style tang into the 1950's those brands are rare.  Also the "Best Cast Steel" stamping was not used by many companies after the 1910's that stamping did continue on a large hardware store's house brand and some English files.