Hi Seabourch,

yes, there is.

Open up the UNIT_PROD file with the Gnome Editor, and find column 20. This determines what eras a unit can be trained in.

You'll see what the options are, and obviously it's EARLY, HIGH, and LATE, but you can also set it to ALL_PERIODS. If you want just two eras, then you need to include quote marks, e.g "HIGH, LATE"