Four Irregular Octahedra
This model was discussed between Aaron and myself here: www.flickr.com/photos/42647582@N07/7399623306/
We both independently designed the model based on our discussion and revealed both versions at the OUSA NYC 2012 convention.
You can see his completed version here: www.flickr.com/photos/42647582@N07/7517840468/
In mine, I have adjusted the shape so that the non-equilateral faces of each octahedron are isosceles. This means there are only 2 unit lengths.
EDIT: See the cheatsheet here: www.flickr.com/photos/8303956@N08/7595366640