noun
brass button; golden button
Refers to a metallic button, typically gold-colored, often found on uniforms such as school blazers.
学生服の金ボタンが光っていた。
The brass buttons on the school uniform were shining.
卒業式のあと、金ボタンを後輩にあげるのが伝統だ。
After the graduation ceremony, it's a tradition to give your brass-button uniform to a junior.
noun
Colloquial metonymy: a male student who wears such a uniform, often used in nostalgic or lighthearted speech.
昔はこの辺りに金ボタンがたくさん歩いていた。
Back in the day, you'd see lots of boys in brass-button uniforms around here.