Hackman butterfly knife
The Hackman butterfly knife (Finnish: Linkkupuukko, "latch-knife") was a type of balisong (butterfly knife) produced by the Finnish company Hackman. The knife was marketed by Hackman as a retkiveitsi ("camping knife") and later as Eräpuukko ("wilderness puukko").
The knives were also sold in the United States, and some researchers state they were issued by the U.S. Central Intelligence Agency during the Vietnam War.
This knife was designed 1959/60, and has been produced ever since. 1981 Hackman sold the original machines and moulds to their formal employee in Sorsakoski region. During the next 20 years the company Pertemet Ltd updated some of the materials to better and more modern style. The blade is nowadays stainless steel. Handle material was matched better to arctic temperatures. Otherwise the taittopuukko or linkkupuukko is exactly the same.
Since 2013 they are manufactured handicrafted by Saga Spirit Ltd in Joensuu, North Carelia region, with the original machinery. The eldest of them is from the year 1955. Mr. Mustonen, later Pertemet Ltd entrereneur, was carrying it inside to the Hackman factory when he was working there. After Hackman the taittopuukko was no longer possible to be called after the company, and since 1981 the puukko has been known by its historical Sorsakoski location as "the Sorsakoskelainen".