In workstation ArcInfo (the PROJECT and related commands), there are two ways
to identify a State Plane zone. The keyword, 'ZONE' uses an old BLM set. That's
the 4526 number for Montana. The keyword, 'FIPSZONE' uses a more recent set
that was defined by NOS/NGS (National Ocean Service/National Geodetic Survey).
At the time, this later set was also put into the queue to get approved as a FIPS
standard which is why we used the word, 'FIPSZONE'.
The move to get the values approved as a FIPS standard has since been dropped.
The 'FIPS' (NGS) set is more complete than the older BLM set. For desktop ArcInfo,
we use the newer set exclusively although we can convert the 'ZONE' numbers into
the NGS values.