Thank you Kubur.
This entry from a WW1 forum makes thinks a bit more clear:
http://lagrandeguerre.1fr1.net/t79229-spahis
Now, I wonder how the surplus stirrups ended up in Calatayud?
For the captions:
Etiquette: "Etriers de Moha ou Hassan el Zaiani tué le 13 Novembre 1914; pris dans sa tente par le moghazni Omar el Zaiani et donné au Cne Ract-Brancaz blessé dans la matinée.
Then, there could be an Italian connection from North Africa to Ottoman?
https://www.metmuseum.org/art/collection/search/32232
The ones at the bottom are said to be Milanese XVIth century.