Officially CZJ's last Sonnar 300/4 (III), got new info! 5 grp / 6 elm I have no knowledge about the lens' version 1 optical design existed.. 300mmF/4 design changed a lot, see > http://zeissikonveb.de/start/objektive/wechselobjektive%201980er/carl%20zeiss%20jena.html