I explained once how stripes on DO-7 [about mid-way between a 1/4w and
1/2w resistors] diode bodies were painted.
You have paint troughs with the colors in use, each has a roller the
width of of the trough, against this you have a roller that tapers to
the width of the band. These in turn roll against a larger rubber wheel
and deposits the paint. This in turn rolls against the R or D.


On diodes the bands also indicated the polarity, so there was an
ingenious way to orientate them.
To measure the breakdown voltage of a diode you apply a small [5
micoamp current]. The diodes were fed into a slot, the current was
applied, if you measued a low voltage it dropped straight down.
If you measured a high voltage it went out the side into a tube that
brought it 180 deg. into the proper orientation.
CP