How to check the password file version

oracle@oric01.oric.no:[PRODDB01]# orapwd describe file=/u01/oracle/product/12201/dbs/orapwPRODDB01
Password file Description : format=LEGACY

If you try to create the password file with a password that is too simple, you may see this error from orapwd:

OPW-00029: Password complexity failed for SYS user : Password must contain at least 8 characters

The format is set to 12.2 by default, and from the orapwd help text there doesn't seem to be anything lower than this.
If you for some reason need to keep an old password which is too simple for today's default settings, you can create a "legacy" password by using the format "legacy". This is not documented in the help text:

orapwd file=u01/oracle/product/12201/dbs/orapwPRODDB01 format=legacy force=Y

Enter password for SYS: