Here's what I've found about these clips. It's all speculation, based on the German name of the part, and its "proximity" to others numerically.
Three in total: here they are:
http://playmodb.org/cgi-bin/textsearch.pl?sortby=description&page=1&text=torso\%2C+inner+support+part\%2C+for+mystery+fi\%3Fures&lang=en&pics=onThe first one,
30 23 2912, has a number in sequence with others that fit 5203 and 5204, Series 1. I'm assuming this is the normal clip that's used for most Fi?ures.
The second,
30 24 8382, has the same German name, therefore is the same mould but could be a different colour. It was released near parts from Series 3 Boys, so I think it's the clear one that belongs to the Robot. I've assigned it to the set, but not as subpart of the figure, yet.
The third,
30 24 8382, has a different German name - "Innenteil-dickb.Mont." - that suggests "thickness", and was released near parts from Series 3 Girls, so I assigned it as a subpart of the pregnant woman. Tim's photo from her, is what I used for the part page. It would make sense that the Mafioso in 7, being fat, would have one. Tim's photo of the Kareteka in Series 6 shows it as well. Fi?ures with Roman legs (I call them "split skirts") are the Roman in 7, the gladiator in 6, the samurai in 5, and the Roman in 4; Tim's photos show the original clip for the samurai, but the "thick" one for the other three.
Clearer or less so?