Ancient Celtic (probably) or Roman brooch (fibula) from an old collection of bronze Celtiberian items

An ancient brooch, known as a fibula, from a collection of Celtiberian items (see more info below). Of note, this brooch still retains quite a lot of coloring and hasn't turned entirely green, like many of them have. It is missing the pin and catch system.

This brooch is from a Celtiberian collection of bronze artifacts, it is made of bronze and it measures approximately 41 x 24 x 9 mm.

Provenance -

We bought a collection of artifacts at auction in Switzerland (La Galerie Numismatique, September 28th, 2024); we are researching each object and offering them for sale individually. You can see the collection in the pictures we posted.

In the course of our investigation, we found that the artifacts had names of places in the Celtiberian region written on them, for example "Salienca". Also, the larger brooch design was unique to the Celtiberians (Google search "Celtiberian Fibula" to see similar examples). We've come to the conclusion that the collection is specific to the Celtiberian era/region.

Wikipedia tells us the Celtiberians "were a group of Celts and Celticized peoples inhabiting an area in the central-northeastern Iberian Peninsula during the final centuries of the BC. They were explicitly mentioned as being Celts by several classic authors (e.g. Strabo)."

Condition -
See pictures. Missing pin/catch system. Some tarnish and black areas (although that may be an underlayment of the goldish color). It is cracked, where the bow meets the catch, and someone has used a piece of paper and glue to hold it together. After taking pictures I added a dab of acid-free PVA glue to make sure it continues to hold as it was starting to get loose. Someone wrote, with a marker, a place name on the inside, but I can't read it.