The Thunderbird has the older style c-shape catch and pin stem. The c-shape catch was used up into the 1920'and 1930s. The thunderbird has not been cleaned or polished. Shows a warmer darkened patina that could be left intact or polished bright.
I will let you decide. The pin shows some age-appropriate wear but overall, nice estate condition. Looks great when worn and will soon become a favorite in your collection.