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

An ancient brooch fragment, known as a fibula, from a collection of Celtiberian items (see more info below). Of note, this was a hefty little brooch, compared with the others in the collection this brooch is quite stout. This brooch is missing the pin/catch system) and four of the six onion shaped protrusions it originally had. A unique design, the bow is more standard to Roman brooches, but the four-onioned plate may reflect the Celtiberian influence.

This brooch is from a Celtiberian collection of bronze artifacts, it is made of bronze and it measures approximately 35 x 33 x 19 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. Bronze is tarnished to green. Missing pin/catch system. Missing four of the six onion shaped protrusions. There are some traces of glue where it was glued to the collection. This one had more iron content than the others, and has some rust.