George Gunn (Crowner of Caithness & Chief of Gunn) in mid 1400's was known as "N’m Braistach-More", which means the "Big Brooched One." Crowner was a powerful Judge like position and it's badge of office was a big silver brooch.

Reference Chapter 5 of The History of Caithness here:
http://www.caithness.org/caithness/c...ness/index.htm

Here's the paragraph:

Chap. 5

This George was a man of commanding influence in the county at the time, and exercised the office of Crowner, from which circumstance he was commonly known by the title of Crowner or Cruner Gunn.Footnote 6 By Highlanders he was called “ N’m Braistach-More,” from a great silver brooch which he wore as the badge or cognisance of his office.
So there's another possible piece of evidence of a gent wearing a brooch. This one is 15th century....