The JIS logo, prior to 2008. Image taken from the Wikipedia.
The visible effect on pens was the new logo that from 1954 was imprinted on pen nibs to guarantee the material out of which they were made. Until that moment, a number of companies advertised theirs as golden when they were merely gold plated. Adopting the logo was, apparently, not compulsory, but Pilot adopted promptly thus pushing other brands to follow suit. However, some brands were reluctant to imprint the logo. With time, its use has decayed and in modern pens is no longer present.
This is the nib of a Pilot R, a popular pen in production for a long time. The JIS logo dates the pen in the late 1950s.
A nice side effect, fifty years later, is that the logo provides an argument to date the pen—any nib with that logo was certainly manufactured after 1954.