Goodgrief - It's still pretty easy to follow - just remember to 'carry the one' (hence EC2xx & EC7xx for a 10-19 ton platform. If that European heavylift project ever gets off the ground, we could perhaps even see an EC9xx designation used, though a 3-engine solution would screw-up the ECxx0/ECxx5 logic...).
widgeon - The BO106 was a widebody BO105 that flew in '73, and was used as a trials ship for the next decade; the BO107 was a 10-seat study that preceded the BK117.
I/C