Some data, showing that "Anything over 3 mm on old working puukko is rare" is a misconception.
Found during excavations
1350-1450: Blade 89 mm, Length 19,5 mm, Thickness 3,8 mm, beveled edge 12 deg.
1400-1450: Blade 92 mm, Length 21,4 mm, Thickness 6,0 mm, beveled edge 16 deg.
1400-1450...