The last letter of their mark series' are what Auran Kultasepät called 'kretsileima'. The closest translation of this is 'filings mark', specifically the waste filings or rubbish left after making a metal object. They were originally associated with being a mark for identifying the responsibility for shoddy and bad work rather than good; an internal quality or control mark if you like. Only later were these given 'master'-mark status.

n = Veikko Nuutinen (1941-1954)

x = Matti Lehto (n.1950-1989)

e = Raimo Roine (1946-1990)

m = Risto Nordling

A = Armas Ahla

A = Anna-Mari Autio (1980s)

B = Aimo Järvinen

C = Reino Lehtinen

E = Aulis Alin

K = Antero Kivi

L = Eero Lehtonen

P = Kauko Stranden (1950s)

P = Pertti Alin (1975-1990s)

R = Antero Rimmanen

U = Sulevi Ojala

Ä = Matti Salonen

Å = Harri Ahokas

UNKNOWN

M, F, J, G, O, H