This is a threaded cap for the wiper washer fluid tank of a citroen C4, it consists of two pieces. The first piece fits by preasure and the second one screws to the first one acting as a cap.
I'm not sure if it can fit other citroen models or even other brands. In case of citroen It's possible that it can fit as some of the parts are shared between models.
If you have another car wher it fits, please let me know to update this.
I hope it's useful !!!
The author hasn't provided the model origin yet.