mag production year by serial-nummer?

[Lewisit]

i'm just curious:

is it possible to roughly tell the time of production by the engraved serial-numbers on the automag-valves?

i have 3 automags here:

CF06858

CF13960

CF55689

any guesses, how old each of these guns ca. is?

are all the same "level"?

thanx


ps: all three of cause shoot like on day one