I think Roy is referencing the number on the "J" head. It's been a
long time but maybe someone can tell us if it was dovetail or round ram
in the mid 50's. There should be another number stamped, I think, on
the lower vertical way surface. BTW the chrome ways were probably an
option at the time your machine was built and for some reason this
feature was slow to catch-on (at least around Chicago from '63 till
around '76).