Thanks for the suggestions so far... I'm not sure it's quite there yet (although amphichiral is an impressive suggestion).... I found 'splice joint' which is common terminology in woodwork. Does any one know if this can then be used across all materials in product design?

Hi, I am hoping someone can help with a technical description I am having trouble putting into words. Basically I am looking for the correct terminology that describes any object that if you have two of said object one can be rotated 180 degrees and fit on to or in to its pair to form one perfectly symmetrical object.
An example sketch can be found here: http://www.jollyg.com/whatsthis.jpg
I was thinking along the lines of rotational symmetrical fitting but it doesn't sound quite right.
Any ideas?