If you are looking for a schematic for version 1.4 or earlier, I’m afraid they do not exist.
Click to download:
Altair-Duino Schematic version 1.5.2
Pro I/O Board Schematic version 1.3
Standard I/O Board Schematic version 1.0
Altair-Duino Schematic version 2.0.4+
Pro I/O Board Schematic version 2.0.4+