Thanks for your help :)
I didn't post pictures because it's your average day to day rs232 cable. Nothing different. Only a reference "940-0024D", but I think it's nothing worth mentioning. I don't even know where these cables come from, maybe with an APC UPS or who knows. One thing is sure: They were not bought separately, so yeah, probably some proprietary stuff.
In the meantime, instead of buying another RS232 to RS232 cable I got this: https://www.amazon.es/gp/product/B00QUZY4WO/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1