Question about early 20th century custom

Factual Questions
1

I recently saw the move First Auto, made in 1928, but set around 1900. Either way “early 20th century” applies. Anyway, at one point, the hero is courting his girlfriend (as they used to say); they’re in an ice cream place having a malt. Anon appears the guy who’s attempting to cut in on the girl. He folds back his lapel to so she can see a button that says: “I’m for you, kid.”. Then he turns to the first guy and displays another button that says “Go way back and sit down”.

!!!

???

Did they really do that in those days?

2

It sounds like it was just a movie joke. I take it that this was a silent movie?

3

It was a silent movie.